ACTIVITY REPORT 2011 - unime.itww2.unime.it/dottoratofisica/ACTIVITY_REPORTS/Report PhD 2011.pdf · 1 issn2038-5889 dottorato di ricerca in fisica universitÀ di messina activity

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ISSN2038-5889

DOTTORATO DI RICERCA IN FISICA

UNIVERSITÀ DI MESSINA

ACTIVITY REPORT

2011

C/O DIPARTIMENTO DI FISICA FACOLTA‘ DI SCIENZE – UNIVERSITÀ DI MESSINA

Lorenzo Torrisi Editore

Activity Report 2011 – Dottorato di Ricerca in Fisica, Università di Messina

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Coordinatore del Dottorato di Ricerca in Fisica

Prof. Lorenzo Torrisi

Editore

Lorenzo Torrisi

Assistenti

Paola Donato

Mariapompea Cutroneo

Rocco Vilardi


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DOTTORATO DI RICERCA IN FISICA

UNIVERSITÀ DI MESSINA

ACTIVITY REPORT

2011

ISSN2038-5889

C/O DIPARTIMENTO DI FISICA FACOLTA‘ DI SCIENZE – Università di Messina

Viale F. Stagno D’Alcontres 312, 98166 S. Agata, Messina

Lorenzo Torrisi Editore

http://ww2.unime.it/dottoratofisica


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INDICE GENERALE

Programma 2

a Giornata di Studio del Dottorato di Ricerca in Fisica dell’Università di Messina

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2a Giornata di studio del Dottorato di Ricerca in Fisica dell’Università di Messina, 8 Nov. 2011

L. Torrisi

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Valutazione nazionale della Qualità della Ricerca 2004-2010 (VQR)

M. C. Aversa

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Dottorato di Ricerca e calcolo Scientifico

D. Magaudda

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On the wavelength shift between near-field peak intensities and far-field peak cross sections in plasmonic

nanostructures

A. Cacciola

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Mass quadrupole spectrometry applied to laser-produced plasmas and microwave ignited plasmas

F. Di Bartolo, L. Torrisi, S. Gammino, F. Caridi, D. Mascali, G. Castro, L. Celona, R. Miracoli, D. Lanaia and

R. Di Giugno

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Fusion reactions in collisions induced by li isotopes on Sn targets

M. Fisichella, A. Di Pietro, A. Shotter, P. Figuera, M. Lattuada, C. Marchetta, A. Musumarra, M.G. Pellegriti,

C. Ruiz, V. Scuderi, E. Strano, D. Torresi, M. Zadro

31

Particle correlations at intermediate energies and the Farcos project

T. Minniti and Farcos/Chimera collaboration

33

Investigation on pseudoscalar meson photoproduction by electromagnetic probe M. Romaniuk, V. De Leo, F. Curciarello, G. Mandaglio, G. Giardina

37

Study of nuclear equations of state: the ASY-EOS experiment at GSI

S. Santoro for ASY-EOS collaboration

41

Premio APP per una Tesi di Dottorato

P. V. Giaquinta

47

PhD e mondo del lavoro: statistiche sul placement post – dottorato

P. Donato

49

An overview of research activities in the physics PhD course

F. Caridi, L. Torrisi

55

Enhanced optical fields for aggregation of metal nanoantennas and label free highly sensitive detection of

biomolecules

B. Fazio, C. D‘Andrea, V. Villari, N. Micali, O. Maragò, G. Calogero and P.G. Gucciardi

61


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Missing resonances at the BGO-OD experiment

F. Curciarello, V. De Leo, G. Mandaglio, M. Romaniuk, G. Giardina

65

Resonant laser absorption and self-focusing effects producing proton driven acceleration from

hydrogenated structures

M. Cutroneo and L. Torrisi

71

Baryon spectroscopy by vector meson photo-production at BGO-OD experiment

V. De Leo, F. Curciarello, G. Mandaglio, M. Romaniuk , G. Giardina

77

Diode lasers for optical trapping applications

R. Sayed, G. Volpe, M. G. Donato, P. G. Gucciardi and O. M. Maragò

81

Interference with coupled microcavities

R. Stassi, O. Di Stefano, S. Savasta

85

Spectral dependence of the amplification factor in surface enhanced Raman scattering

C. D‘Andrea, B. Fazio, A. Irrera, P. Artoni, O.M. Maragò, G. Calogero and P.G. Gucciardi

89

Photoluminescence of a Quantum Emitter in the Center of a Dimer Nanoantenna: Transition from the

Purcell effect to Nanopolaritons

N. Fina, A. Ridolfo, O. Di Stefano, O. M. Maragò ,S. Savasta

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Lateral Diffusion of DPPC and octanol in a Lipid Bilayer Measured by PFGE NMR Spectroscopy

S. Rifici

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Chemical equilibration of the quark gluon plasma

F. Scardina, M. Colonna, V. Greco, M. Di Toro

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A study about dynamic models on phospholipids

A. Trimarchi

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Ultrafast optical control of light-matter interaction and of wave-particle duality

R. Vilardi, S. Savasta

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Seminari (invited) del Dottorato di Ricerca in Fisica, Effettuati nel 2011

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Organizzazione del Dottorato di Ricerca in Fisica dell’Università di Messina,

Ciclo (XXVI)

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Pubblicazioni 2011 degli studenti del Dottorato di Ricerca in Fisica dell’Università di Messina

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Foto 2a Giornata di Studio del Dottorato di Ricerca in Fisica dell’Università di Messina

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Indice Autori

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8 Novembre 2011

Biblioteca Centralizzata

V.le F. Stagno D’alcontres 31, S. Agata, Messina

http://ww2.unime.it/dottoratofisica

2a Giornata di Studio

del Dottorato di Ricerca in

Fisica dell’Università di

Messina


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Comitato Organizzatore

Prof. L. Torrisi

Dr.ssa P. Donato

Dr.ssa M. Cutroneo

Dr. R. Vilardi

Comitato Scientifico

Prof. G. Carini

Prof. P. Giaquinta

Prof. G. Giardina

Prof. G. Maisano

Prof. D. Majolino

Prof. L. Torrisi

Giornata Organizzata dal

Collegio Docente

del Dottorato di Ricerca in Fisica

e sponsorizzata dall’ Università di Messina

Sito della Giornata di Studio:

Biblioteca Centralizzata della Facoltà di

Scienze dell’Università di Messina, Viale F.

Stagno D’alcontres 31, 98166 S.- Agata,

Messina


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9.15 Relazioni di Apertura Saluti del Preside della Facoltà di Scienze MM.FF.NN.

Prof. G. Maisano, Direttore del Dipartimento di Fisica

Prof. L. Torrisi, Coordinatore del Dottorato di Ricerca

in Fisica

Prof. D. Majolino, Coordinatore dei CdL in Fisica e

Fisica Magistrale

Prof. F. Neri, Direttore Dip.to di Fisica della Materia

ed Ingegneria Elettronica

Prof.ssa M. C. Aversa, Delegata alla Ricerca

Scientifica e Tecnologica dell‘Università

Dr.ssa D. Magaudda Responsabile dell‘Area Sistema

Informativo per l‘Analisi dei Dati e Calcolo Scientifico

Dottorato Ciclo XXV Presiede: Prof. G. Carini

10.00 A. Cacciola (On the wavelength shift between

near-field peak intensities and far-field peak

cross-sections in plasmonic nanostructures)

10.20 F. Di Bartolo (Mass Quadrupole Spectrometry

applied To Laser-Produced Plasmas and

Microwave Ignited Plasmas)

10.40 M. Fisichella (Fusion reactions and neutron

transfer in collisions induced by Li isotopes on Sn

targets)

11.00 T. Minniti (Particle correlations to intermediate

energies and the Farcos Project)

11.20 M. Romaniuk (Investigation on pseudoscalar

meson photoproduction by electromagnetic probe)

11.40 S. Santoro (Study of nuclear equations of state:

the ASY-EOS experiment at GSI)

12.00 Interventi degli Enti di Ricerca Presiede: Prof. G. Giardina

Dr. G. Cuttone, Direttore dei LNS, Catania

Dr. C. Vasi, Direttore IPCF-CNR, Messina

Dr. A. Pagano, Direttore Sez. INFN, Catania

Prof. S. Albergo, Direttore del CSFNSM

Presiede: Prof. P. Giaquinta

Premiazione Tesi di Dottorato di Ricerca in

Fisica, Patrocinata dall‘Accademia Peloritana

dei Pericolanti

12.30 Dr. A. Ridolfo (Quantum Optical

Properties of strongly Coupled Systems)

Presiede Prof.: G. Mondio

15.00 Dr.ssa P. Donato, Manager Didattico PhD

(PhD e mondo del lavoro: statistiche sul

placement post-dottorato)

15.15 Dr. F. Caridi, Facoltà di Scienze – ME

(An overview of research activities in the physics

PhD course)

15.30 Dr.ssa B. Fazio, IPCF-CNR (Enhanced

optical fields for aggregation of metal

nanoantennas and label free highly sensitive

detection of biomolecules )

Ciclo XXVI- Presentazione posters 15.45 Presiede Prof. L. Torrisi

F. Curciarello (Missing resonances at the BGO-

OD experiment)

M. Cutroneo (Resonant laser absorption and self-

focusing effects producing proton driven

acceleration from hydrogenated structures)

V. De Leo (Baryon spectroscopy by vector meson

photoproduction at BGO-OD experiment)

R. Sayed (Diode lasers for optical trapping

applications)

R. Stassi (Interference with coupled

microcavities: optical analog of spin 2 rotations)

Ciclo XXIV- Presentazione posters 16.25 Presiede Prof. D. Majolino

C. D’Andrea (Spectral dependence of the

amplification factor in surface enhanced Raman

spectroscopy)

N. Fina (Photoluminescence of a quantum

emitter in the center of a dimer nanoantenna:

transition from the Purcell effect to

nanopolaritons)

S. Rifici (Structural changes of lipid bilayers by

the addiction of short-chain alcohols)

F. Scardina (Chemical equilibration of the

quark gluon plasma)

A. Trimarchi (A study about dynamic models

on phospholipids)

R. Vilardi (Ultrafast optical control of light-

matter interaction and of light wave-particle

duality)

17.15 Interventi di chiusura da parte del Collegio

Docente – Conlusione dei Lavori


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Prof. L. Torrisi

2a GIORNATA DI STUDIO DEL DOTTORATO DI RICERCA IN FISICA

DELL’ UNIVERSITÀ DI MESSINA

MESSINA, 8 NOVEMBRE 2011

Lorenzo Torrisi

Coordinatore del Dottorato di Ricerca in Fisica

Dip.to di Fisica, Università di Messina

V.le F. Stagno D’Alcontres 31, 98166 S. Agata, Messina

La seconda giornata

di studio del Dottorato

di Ricerca in Fisica

dell‘Università di

Messina trova in questa

seconda manifestazione

un altro particolare

momento di riflessione

scientifica di notevole

rilevanza, di riunione

collegiale accademica,

meeting di discussione

su aspetti di Fisica,

consuntivi e

proponimenti, che

coinvolge i Dottorandi della Scuola, il Collegio

Docente, gli Organi competenti della Nostra Facoltà e

dell‘Università nonché delle istituzioni scientifiche che

collaborano col Dottorato stesso, come l‘Istituto

Nazionale di Fisica Nucleare e il Consiglio Nazionale

delle Ricerche.

Il Collegio Docente, la comunità dei fisici, quella dei

colleghi di altre aree scientifiche e tutti i nostri

collaboratori potranno cogliere l‘occasione di questa

giornata per informarsi sullo stato dei lavori del

Dottorato di Ricerca in Fisica, orgoglio della Nostra

Università. Mediante questo appuntamento sarà

possibile conoscere le tematiche delle ricerche in Fisica

che si stanno attualmente sviluppando presso il Nostro

Ateneo, i progetti che coinvolgono collaborazioni con

altre sedi universitarie, centri di ricerca e laboratori

esteri, le attività svolte nei laboratori di Messina e in

altre sedi collegate. Tali laboratori vedono

l‘avvicendarsi continuamente dei nostri dottorandi in

ricerche di ampio respiro internazionale e spesso

diventano loro sede di lavoro post-doc.

I risultati più innovativi che con essi vengono

ottenuti sono stati, e continuano ad esserlo, oggetto di

pubblicazioni su riviste ISI con ricadute non solo nel

mondo della ricerca e della didattica ma anche in

quello sociale. Molte ricerche svolte in seno al

dottorato sono infatti pubblicate su riviste ad alto

fattore di impatto, molte collaborazioni vengono

effettuate con gruppi di ricercatori dei migliori

laboratori europei ed extraeuropei, molti risultati

trovano applicazione in campo sanitario e ambientale e

molti nostri dottori di ricerca trovano occasione di

lavoro in questi centri di eccellenza.

Partecipare a questa giornata ci permetterà di

conoscere meglio le attività di ricerca di gruppi a noi

vicini, di una nuova generazione di giovani fisici, e ci

potrà permettere di instaurare un discorso scientifico

creativo e costruttivo con loro, un‘occasione che

almeno una volta all‘anno ha motivo di esistere.

Logo Università di Messina

Nel mio ruolo, colgo l‘occasione per ricordarvi che il

Dottorato di Ricerca rappresenta il massimo titolo per

la preparazione scientifica che l‘Università può

conferire ai propri studenti. Oltre la laurea breve, la

laurea magistrale, le Scuole di Specializzazione ed i

Masters, il Dottorato offre possibilità di apprendimento

uniche. Esso si basa non solo sulle lezioni di un

Collegio Docente altamente qualificato ed appropriato

ma anche su una periodica serie di seminari

specialistici tenuti in un contesto Nazionale ed

Internazionale che investono i vari Curriculum del

Dottorato. Attualmente 31 docenti fanno parte del

collegio, 17 sono i dottorandi, 4 i curricula di studio e

ogni mese due esperti sono invitati a tenere seminari

specialistici di interesse curriculare.

I campi di rilievo sono quelli della Struttura della

Materia, della Fisica della Materia Soffice e dei

Sistemi Complessi, della Fisica Nucleare e della Fisica

Applicata all‘Ambiente, ai Beni Culturali e al Settore

Bio-Medico. E‘ in questi ampi settori che il nostro


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La ricerca scientifica

dottorando viene portato a svolgere attività di ricerca,

usufruendo di una serie di Laboratori altamente

adeguati nei quali ha l‘opportunità di operare dando un

proprio contributo. I laboratori dell‘Accademia delle

Scienze della Repubblica Ceca di Praga, l‘Istituto di

Fisica dei Plasmi e di Microfusione Laser di Varsavia, i

laboratori GSI di Darmstadt, i laboratori Nazionali

dell‘INFN, l‘Istituto di Ricerca Nucleare Ucraino INR,

l‘Istituto di Fisica Nucleare Skobeltsyn di Mosca e

quello JINR di Dubna, sono solo alcuni dei vari

laboratori di eccellenza con i quali il Nostro dottorato

può svolgere una continua attività di ricerca e avvalersi

di una collaborazione con scambio di studenti e

docenti. Collaborazioni rese solide attraverso accordi e

protocolli ufficiali che sono stati voluti da alcuni

componenti del Nostro Collegio Docente. A loro va un

plauso per queste collaborazioni che non nascono dal

nulla ma da un intenso, attivo e continuo lavoro,

spesso sottovalutato, grazie al quale il nostro Dottorato

può emergere e avere un respiro a livello internazionale

e l‘Università di Messina essere menzionata nel

mondo.

Laboratorio di fisica dei Plasmi Laser, Dip.to

Fisica, Messina

I dottorandi hanno la possibilità di essere inseriti in

progetti di ricerca di front-end, di partecipare a lavori

scientifici di prestigio e di redigere delle tesi inedite,

originali e utili. Per questo sono guidati durante il loro

percorso verso corsi e scuole di formazione

internazionali che permettono loro di ottenere una più

mirata specializzazione sulla tematica di loro maggiore

interesse. Ma il loro lavoro ha bisogno di essere

maggiormente conosciuto e divulgato. Ciò avviene non

solo attraverso le pubblicazioni di lavori scientifici ma

anche mediante altri canali, come questa giornata di

studio nella quale gli è consentito, di esprimersi e

dialogare per avere i giusti input e suggerimenti e un

maggiore sostegno durante la sua formazione,

necessari all‘ottenimento di maggiori riconoscimenti e

consensi scientifici. Ricordo ai dottorandi che ogni loro

risultato, seppur minimo, è prezioso e come in un

grande mosaico costituisce un piccolo pezzo che si

aggiunge a tanti altri che sono venuti e che verranno e

che permettono di ampliare le conoscenze umane.

Abituarsi a trasferire le proprie conoscenze, ad

intercalarle in problematiche più generali, a

completarle con altre al fine di poter estrapolare leggi e

teorie, è una attività che il dottorando andrà sempre più

approfondendo sia durante il dottorato di ricerca che

dopo, con l‘esperienza post-doc. La ricerca mette in

moto energie e stimoli di tale vitalità che il

meccanismo economico ne trae vantaggio, come una

macchina ben alimentata. L‘innovazione frutto della

ricerca ha dunque una ricaduta pratica e concreta anche

sulla ricchezza delle nazioni.

Ma proprio su questo punto, si impone qualche altra

mia considerazione che purtroppo ricalca quanto già

detto l‘anno scorso.

Ancora oggi in Italia la ricerca scientifica è, come è

noto, poco finanziata e i ricercatori sono mortificati dai

finanziamenti quasi inesistenti. Inoltre la crisi italiana

ed europea nel campo dell‘occupazione giovanile rende

difficile l‘utilizzo appieno delle capacità che il

dottorando ha appreso e spesso egli trova grosse

difficoltà di inserimento nel mondo della ricerca e del

lavoro post-doc. Sempre più spesso i nostri dottorandi

debbono purtroppo trasferirsi all‘estero regalando ad

altre realtà le esperienze acquisite. In questo contesto la

giornata di studio attuale vuole rappresentare una

denuncia alla nostra società ed ai nostri politici

cercando di sensibilizzarli maggiormente verso

l‘importanza della ricerca scientifica in uno stato

funzionale.

Tuttavia qualcosa si sta muovendo, visto che

recentemente il Ministro dell‘Istruzione,

dell‘Università e della Ricerca ha emanato un

regolamento recante i nuovi criteri generali per la

disciplina del dottorato di ricerca. Una meritata

attenzione che ci fa sperare in un futuro migliore, come

verrà tra poco approfondito dalla delegata alla Ricerca

Scientifica e Tecnologica dell‘Università di Messina,

Professoressa Maria Chiara Aversa e dalla

Responsabile dell‘Area Sistema Informativo per

La ricerca scientifica


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Doctor of Phylosophy

l‘Analisi dei Dati e Calcolo Scientifico, Dottoressa

Dora Magaudda.

Inoltre tante iniziative sono in corso per agevolare il

finanziamento da parte della comunità europea di

specifici progetti di ricerca per i giovani post-doc.

Quest‘anno il Dottorato di Ricerca in Fisica ha

ricevuto solo due borse universitarie, una terza

l‘abbiamo ottenuta grazie ai fondi INFN, purtroppo

non possiamo avere di più, neppure per studenti

stranieri non europei. E‘ un peccato che il nostro

dottorato di ricerca, debba subire un decremento di

elementi, nonostante il numero crescente di aspiranti

studenti sia della sede che da fuori sede.

Ma noi non ci fermeremo per queste difficoltà

perché crediamo profondamente nella formazione e

nella Ricerca che in Italia può realizzarsi al meglio

anche con le avversità che si spera essere solo

momentanee. E per questo ideale oggi siamo qui e

presenteremo le nostre attività che reputiamo essere

alla base della nostra esperienza di fisici. E‘ grazie a

questi ideali che il nostro Dottorato può permettere le

sue formative e molteplici attività e mira a promuovere

e premiare i giovani con le migliori redazioni di Tesi e

di risultati conseguiti, come oggi sarà evidenziato.

1° Report del Dottorato di Ricerca in Fisica,

2010

Vi ricordo che, secondo quanto approvato dall‘

ultima riunione del Collegio docente, che i dottorandi

del secondo anno dovranno presentare un intervento

sul loro lavoro di tesi mentre i dottorandi del primo e

terzo anno un poster e un sintetico sunto. I lavori

scientifici che i dottorandi esporranno in questo

incontro, sia come contributo orale che come poster,

nonché i vari interventi che gli invitati presenteranno,

saranno raccolti nel secondo Report del Dottorato di

Ricerca in Fisica dell‘Università di Messina, che sarà

pubblicato a breve e che rappresenterà un altro

documento duraturo nel tempo, una vera e propria

pubblicazione per il dottorando, e una pubblicazione

annuale del Dottorato, depositata presso la nostra

biblioteca, con numero ISSN già assegnato.

RingraziandoVi per l‘attenzione dedicatami, auguro

a tutti voi, colleghi, dottorandi e partecipanti, un buon

lavoro.

Il Coordinatore del Dottorato di Ricerca

Prof. Lorenzo Torrisi


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VALUTAZIONE NAZIONALE DELLA QUALITÀ DELLA RICERCA

2004-2010 (VQR)

Maria Chiara Aversa

Delegata del Rettore dell’Università di Messina per la ricerca in area scientifico-tecnologica

Il 7 novembre 2011 è stato pubblicato il bando

ufficiale di partecipazione alla Valutazione della

Qualità della Ricerca 2004-2010 (VQR 2004-2010)

(http://www.anvur.org/sites/anvur-

miur/files/bando_vqr_def_07_11.pdf).

L‘inizio dell‘esercizio di valutazione

nazionale era atteso da tempo, ma probabilmente esso è

stato rinviato più volte come conseguenza del

passaggio dal Comitato Nazionale per la Valutazione

del Sistema Universitario (CNVSU) all‘Agenzia

Nazionale di Valutazione del sistema Universitario e

della Ricerca (ANVUR). All‘epoca della pubblicazione

del DM n. 8 del 19 marzo 2010 avente per oggetto

―Linee guida VQR 2004-2008‖

(http://civr.miur.it/vqr_decreto.html) il progetto di

valutazione nazionale era limitato a cinque anni e

l‘acronimo VQR corrispondeva appunto a

―Valutazione Quinquennale della Ricerca‖. A causa del

notevole postergarsi della data d‘inizio, è stato deciso

di includere altri due anni, e si è giunti così al

significato attuale dell‘acronimo.

Figura 1

A metà del 2011 si è insediato il consiglio

direttivo dell‘ANVUR (figura 1) costituito da 7

componenti, tutti di estrazione universitaria, presieduto

da Stefano Fantoni, professore ordinario di FIS/04

(Fisica nucleare e subnucleare) della SISSA di Trieste,

cui si affiancano professori appartenenti alle aree 06

(Scienze mediche), 07 (Scienze agrarie e veterinarie),

09 (Ingegneria industriale e dell‘informazione), 13

(Scienze economiche e statistiche) e 14 (Scienze

politiche e sociali). La figura 1 è congegnata in maniera

da mettere in evidenza la distribuzione geografica delle

strutture universitarie da cui provengono i 7

componenti del consiglio direttivo, e la distribuzione di

genere (cerchi azzurri/rosa): sono solo 2 le donne nel

consiglio direttivo, uniche 2 rappresentanti della

macroarea umanistica, Fiorella Kostoris Padoa

Schioppa e Luisa Ribolzi, entrambe in pensione, la

prima dall‘Università di Roma La Sapienza e la

seconda dall‘Università di Genova. Si tratta di dati che

dovrebbero suscitare qualche riflessione.

La VQR 2004-2010 è coordinata da Sergio

Benedetto (figura 1), professore ordinario di ING-

INF/03 (Telecomunicazioni) presso il Politecnico di

Torino. Il bando di partecipazione alla VQR del 7

novembre 2011 ha lievemente modificato il contenuto

dell‘art. 5 del DM n. 8 del 19 marzo 2010 avente per

oggetto ―Linee guida VQR 2004-2008‖: in particolare

(a) gli articoli scientifici da proporre per la valutazione

potranno essere stati pubblicati anche su riviste prive di

ISSN e (b) potranno essere proposte anche le

traduzioni. Visto che già dal 2010 l‘Ateneo di Messina

prende in considerazione per le proprie valutazioni

interne soltanto i prodotti citati dall‘art. 5 di cui sopra,

bisognerà proporre al Senato accademico un‘eventuale

delibera di adeguamento.

L‘ANVUR ha inoltre pubblicato la lista dei

presidenti dei Gruppi di Esperti della Valutazione

(GEV) (figura 2), uno per ciascuna delle 14 aree CUN.

Entro la fine di novembre verrà approvata e pubblicata

la composizione dei 14 GEV insieme con i criteri

sottostanti alla selezione degli esperti. In analogia alla

1, anche la figura 2 è congegnata in maniera da mettere

in evidenza la distribuzione geografica delle strutture di

ricerca da cui provengono i 14 presidenti dei GEV, e la

distribuzione di genere: ancora una volta soltanto 2

donne, Clara Nervi, professore straordinario presso

http://www.anvur.org/sites/anvur-miur/files/bando_vqr_def_07_11.pdf

http://www.anvur.org/sites/anvur-miur/files/bando_vqr_def_07_11.pdf

http://civr.miur.it/vqr_decreto.html


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l‘Università di Roma La Sapienza per l‘area 05

(Scienze biologiche) e Maria Teresa Giaveri per l‘area

10 (Scienze dell'antichità, filologico-letterarie e

storico-artistiche), attualmente professore ordinario

presso l‘Università di Torino e che ha insegnato

―Lingua e letteratura francese‖ presso l‘Università di

Messina nel periodo 1994-1997.

E‘ necessario evidenziare le scadenze

temporali che l‘Università dovrà rispettare nel prendere

parte all‘esercizio della valutazione nazionale della

ricerca:

a) certificazione elenchi CINECA/MIUR

soggetti valutabili (30 dicembre 2011);

b) verifica elenchi doc, postdoc, assegnisti,

specializzandi area medica (06) (31 marzo

2012);

c) trasmissione informazioni mobilità nel

settennio (31 marzo 2012);

d) trasmissione prodotti di ricerca (30 aprile

2012);

e) rapporto di autovalutazione (NV/Rettore) (31

maggio 2012);

f) trasmissione brevetti, spin-off, finanziamenti,

ecc… + elenco nuovi Dipartimenti con

afferenti (31 maggio 2012).

Figura 2

Il rapporto finale dell‘ANVUR dovrebbe essere

disponibile entro il 30 giugno 2013.

Tra le innovazioni più significative e gli

aspetti più rilevanti del bando VQR del 7 novembre

2011 rispetto ai documenti precedentemente a

disposizione, si segnala:

a) è stato eliminato il coefficiente di

proprietà per i prodotti presentati da più di

una struttura;

b) è stato eliminato l‘indicatore di proprietà

dei prodotti eccellenti;

c) è stato eliminato il vincolo per le strutture

di rispettare l‘ordine di priorità dei

prodotti indicato dagli autori;

d) globalmente su tutte le aree, almeno la

metà più uno dei prodotti saranno

sottoposti a peer review;

e) la precedente valutazione VTR 2001-

2003 si è basata su circa 17.000 prodotti,

mentre l‘attuale VQR è dimensionata

intorno a 200.000 prodotti.

Appare opportuno concludere questo

contributo citando testualmente la frase di chiusura del

messaggio di accompagnamento

(http://www.anvur.org/?q=schema-dm-vqr-definitivo)

del bando VQR del 7 novembre 2011 a firma di Sergio

Benedetto (figura 1): ―Vi rinnovo l‘augurio di buon

lavoro, nella certezza che insieme affronteremo e

risolveremo i molti problemi che si presenteranno

strada facendo‖. Effettivamente solleva qualche

perplessità questa mal celata mancanza di sicurezza

nella effettività delle procedure, ma, ancora una volta,

….. l‘Università italiana ce la farà!

http://www.anvur.org/?q=schema-dm-vqr-definitivo


15

DOTTORATO DI RICERCA E IL CALCOLO SCIENTIFICO

Dora Magaudda

Sistemi Informativi per l’Analisi dei dati d’Ateneo e Calcolo Scientifico CECUM

Università di Messina

Il Dottorato di Ricerca è stato istituito in Italia solo

nel 1980 (legge 21 febbraio 1980, n. 28, D.P.R. 11

luglio 1980, n. 382), e rappresenta il più alto grado

d‘istruzione ottenibile nel sistema universitario italiano

e conferisce la qualifica di ―Dottore di Ricerca‖, è il

più alto titolo accademico conferibile nell‘ordinamento

della Repubblica Italiana.

Nel corso degli anni, l‘andamento di tali corsi è stato

attentamente valutato non solo dal MiUR ma anche da

tutti i sistemi ufficiali di valutazione, compresi la

CRUI, il CNVSU e i Nuclei.

La CRUI definisce ―il Dottorato come il terzo livello

di formazione universitaria ed è il grado più alto di

specializzazione offerto dalle Università sia per le

carriere accademiche e di ricerca sia per quelle nel

mondo produttivo, in particolare di quello attento

all‘innovazione. È pertanto necessario che il valore del

dottorato sia alto e, come tale, riconosciuto

internazionalmente. La formazione dottorale non può

che essere fatta con e per la ricerca e quindi richiede,

per il suo espletamento, una documentata attività di

ricerca ad alto livello….

Il dottore di ricerca deve diventare il prodotto finale

e più specializzato che l‘università dà alla società per

una classe dirigente preparata e consapevole‖.

Il nuovo statuto dell‘Università di Messina ha posto

l‘istituzione dei Dottorati di Ricerca tra i suoi interessi

primari: tra gli organi di Governo è stato inserito, tra

gli altri, il Collegio dei Coordinatori delle Scuole di

Dottorato.

Problematiche rilevate sui dottorati di ricerca

e indicazioni ministeriali per le loro soluzioni

Già nel 2002-2003, il CNVSU auspicava che fossero

incoraggiati alcuni comportamenti volti a

salvaguardare le finalità del Dottorato di Ricerca,

chiedendo ai Nuclei di Valutazione di monitorarle:

a) contenimento dell’eccessiva frammentazione,

ciò potrebbe infatti comportare:

a. una docenza e un programma formativo

inadeguati

b. uno scarso numero d‘iscritti e di borse.

Così come con la 509 si è avuta una larga

proliferazione di Corsi di Studio non facilmente

spendibili nel mondo del lavoro, anche per i Dottorati

di Ricerca ci si è trovati di fronte ad una situazione

simile. Per tali ragioni, il CNVSU è sempre stato

favorevole a iniziative di accorpamento, che portino

alla costituzione di Scuole di Dottorato.

Questo è un compito abbastanza semplice per i

Nuclei, laddove si riscontrino dottorati che nel loro

piano di studi abbiano aree disciplinari sovrapponibili;

ma quando questa sovrapposizione non esiste o

richiederebbe conoscenze approfondite, diviene

necessaria una peer review che non è sempre

effettuabile da parte dei Nuclei stessi.

b) concentrazione in un‘unica sede delle attività

didattiche dei dottorati consorziati.

Questa valutazione è abbastanza semplice per i

Nuclei

c) opportuna ricerca di fonti esterne di

finanziamento, onde consentire la creazione di figure

professionali appropriate a creare sbocchi

occupazionali, laddove, soprattutto, le fonti di

finanziamento esterne siano erogate da Aziende

interessate alla ricerca. Altrimenti, c‘è il rischio che il

titolo possa essere considerato come una semplice

estensione del percorso formativo della laurea.

Questa valutazione è abbastanza semplice per i

Nuclei

d) creazione di una spinta all‘internazionalizzazione,

con la creazione di percorsi preferenziali per l‘accesso

di studenti stranieri o di altre Università, tramite

l‘istituzione di borse apposite e incentivando la

collaborazione con Atenei stranieri.

Anche questa valutazione è abbastanza semplice per

i Nuclei, ma solo in fase di Consuntivo, in quanto, nella

fase di Attivazione o di Rinnovo di un Dottorato di

Ricerca, i collegamenti con altre Università ed Enti,

italiani o stranieri, non possono ancora essere

formalizzati, dato che la valutazione del Nucleo

avviene prima della decisione della Governance

dell‘Ateneo sui dottorati da attivare e sul numero di

borse d assegnare ad ognuno.


16

Negli anni passati, a partire dall‘esercizio 2002, si è

avuta una ripartizione del 20% di finanziamento alle

Università per i Dottorati di Ricerca che rispondessero

ad alcuni requisiti precisi, che sono stati recepiti anche

dal Nucleo di Valutazione dell‘Università di Messina e

saranno discussi in seguito.

Essendo stata concessa grande autonomia alle

università che decidono:

• L‘istituzione dei corsi di dottorato

• Le modalità di accesso e conseguimento del

titolo

• Gli obbiettivi formativi ed il relativo

programma di studio

• La durata

• Il contributo per l‘accesso e la frequenza

• Le modalità di conferimento e l‘importo delle

borse di studio.

il problema che si è prospettato è stato della

impossibilità di definire in maniera chiara e univoca

per tutte le Università i termini di attivazione dei

Dottorati.

I Nuclei si sono trovati di fronte al problema di

standardizzare (almeno a livello di Ateneo) le

valutazioni dei Dottorati di Ricerca.

ll Nucleo di Messina ha stabilito che, laddove fosse

esprimibile con un indicatore un requisito ministeriale,

di considerarlo come indispensabile per l‘assegnazione

di un valore, affinché l‘Ateneo potesse concorrere a

questa quota di finanziamento

La legge 30 Dicembre 2010, n. 240

Con l‘introduzione della nuova legge del 30

Dicembre 2010, n. 240, si è arrivati alla proposta di una

nuova e più ampia visione dei corsi di Dottorato,

rivisitata anche in base alle esperienze pregresse.

Anche in questo caso, si pone l‘accento sulla

partecipazione dei Dottorandi ai gruppi e ai progetti di

ricerca e si richiede di esaminare la necessità di una

valutazione periodica della produzione scientifica dei

dottorandi. Questa valutazione si dimostra piuttosto

problematica sin da oggi, in quanto tra le varie aree

scientifiche-disciplinari, e soprattutto tra le macro-aree

umanistiche e scientifiche, si ha una notevole

differenziazione nella preparazione alla ricerca dei

dottorandi stessi. Un esempio per tutti è quello dei

dottorati in aree letterarie, dove il dottorando prepara la

sua tesi, che deve essere inedita, in genere tramite una

monografia e non tramite più articoli su rivista o altro

come avviene nelle aree scientifiche. Questo modus

operandi porta alla pubblicazione della tesi solo dopo

l‘esame finale di Dottorato: ne consegue una forte

difficoltà per i Nuclei nella valutazione annuale dei

consuntivi dei dottorati di ricerca di questo tipo.

Un‘altra differenza fondamentale si può riportare a

proposito della numerosità degli autori: in generale,

nelle pubblicazioni scientifiche, si hanno

collaborazioni tra più settori scientifici disciplinari e/o

più macro-aree, ne consegue che il numero di autori

può essere molto superiore a quello di coloro che

hanno produzioni eminentemente umanistiche (in

generale un solo autore).

Il Nucleo di Messina ha recepito le difficoltà espresse

dai Coordinatori delle Aree Umanistiche, suddividendo

i risultati delle valutazioni nelle due macro-aree

distinte; ma nonostante ciò esistono problematiche non

risolvibili semplicemente con una standardizzazione

del calcolo degli indicatori.

Un altro punto importante cui si fa espressa

menzione è che non può essere accettabile la

consecuzione del titolo di dottore di ricerca oltre i 30

anni, dato che dovrebbe essere possibile entrare nella

fase post-doc o lasciare l‘Università attorno ai 26-27

anni, evitando un inserimento tardivo nella realtà

professionale.

Il Nucleo di Messina probabilmente modificherà il

calcolo dell‘indicatore, per quanto lo abbia già fatto in

passato differenziando i punteggi dei dottorandi senza

borsa, con borsa e con borsa di altra amministrazione.

E‘ necessario sottolineare che la legge non prevede

risorse sufficienti per la propria applicazione, quindi

neanche per il dottorato di ricerca: allo stato attuale il

taglio di oltre il 30% verificatosi nell‘ultimo triennio

potrebbe arrivare a raggiungere circa il 50% dei posti

messi a concorso. Si presume che i circa 12.000

dottorandi possano ridursi a meno di 6.0001: ciò

significherebbe una consistente riduzione del sistema

dell‘Alta Formazione.

Si ipotizza, dal testo della legge, che si avrà una forte

incentivazione dell‘istituzione dei Dottorati senza borsa

(senza, per altro, consentire almeno una notevole

riduzione delle tasse di iscrizione) anche se

l‘interpretazione della disciplina sulle borse di studio è

controversa, pur essendo rimodulato l‘importo minimo

della borsa stessa, che in Italia, rispetto ad altri paesi

europei è molto contenuto.

L’Art. 7 – Interventi di cooperazione interuniversitaria internazionale strutturata prevede che solo 4.000.000€ vengano destinati a consolidare e incentivare interventi di università italiane, di studenti, laureati e dottorandi provenienti da Paesi extraeuropei

1 Questi dati sono messi a disposizione dall‘ANDI


17

in linea con le politiche ministeriali di cooperazione internazionale.

Il numero minimo di borse di dottorato passa da 3 a

6: ma non è chiaro se quest‘ultimo numero è da

intendersi solo per le Scuole di Dottorato o per i corsi

di dottorato. In quest‘ultimo caso, quelli attivabili

presso ciascuna Università dovrebbero essere molto

meno numerosi, soprattutto nei casi in cui la

reperibilità di risorse esterne, fortemente dipendente,

com‘è ovvio, dal bacino geografico su cui insiste la

singola Università, è problematico.

Il Nucleo, anche in questo caso, può giudicare il

numero di borse solo dopo la loro assegnazione, quindi

in fase di consuntivo

La legge chiede anche una valutazione dell‘impatto

professionale del titolo.

Il precedente Nucleo di Valutazione aveva inserito

nelle sue valutazioni una tabella in cui si chiedeva ad 1

anno, a due e a tre quale fosse l‘attività lavorativa

intrapresa dal dottorando e se fosse coerente con il

percorso di studi. I dati ricevuti in risposta sono

piuttosto scarni e quindi non significativi, perché non

sempre era possibile contattare i dottorandi stessi

Attivazione dei corsi di dottorato e ruolo del

nucleo

Come si è già detto, i Nuclei di Valutazione hanno

dovuto, nel corso degli anni, giudicare i Dottorati di

Ricerca in base a determinati requisiti, che la 240 ha

reso più stringenti. Il Nucleo di Messina ha concepito

una scheda di richiesta rinnovo/nuova attivazione ed

una di Consuntivo che contenesse tutte le informazioni

necessarie alla valutazione dei Dottorati di Ricerca. In

tal modo, avrebbe potuto effettuare le sue valutazioni

nella maniera più corretta in base alle indicazioni

ministeriali.

A tale scopo, ha chiesto alla propria Referente

Informatica, capo Area Sistemi Informativi per

l‘Analisi dei dati d‘Ateneo e Calcolo Scientifico, la

creazione di un software apposito. Il risultato è stato

considerato molto soddisfacente sia dal Nucleo che

dall‘utenza, per la semplicità d‘uso e le facilities

inserite che lo rendono intuitivo ed efficace.

In sintesi il software si compone di sei parti

fondamentali:

1. Compilazione della scheda di richiesta

rinnovo/nuova attivazione da parte del Coordinatore

2. Compilazione della scheda di consuntivo per

ogni ciclo attivo da parte del Coordinatore e dei

Dottorandi

3. Attestazione della correttezza delle

dichiarazioni informatizzate da parte dell‘Ufficio

Dottorandi che convalida, in base al cartaceo presentato

dai Coordinatori, quanto da loro stessi dichiarato2

4. Attestazione della validità delle dichiarazioni

dei dottorandi da parte del Nucleo di Valutazione3

5. Procedura automatizzata di calcolo dei

punteggi degli indicatori4

Procedura di visualizzazione dei punteggi degli

indicatori di tutti i dottorati. La procedura consente la

visualizzazione di tutti i dettagli ed è visibile a tutti i

Coordinatori.

Gli indicatori considerati sono 8 e rispecchiano, dove

possibile, le richieste del Ministero in maniera

dettagliata, ovvero i criteri concordati con la

Governance d‘Ateneo laddove quelli ministeriali siano

nebulosi o non ben descritti.

Rispetto ai primi calcoli, sono state apportate

modifiche delle quali via via si sentiva il bisogno,

dettate sia dalle differenze tra la conduzione dei

dottorati di ricerca (per esempio tra le due macro aree

Umanistica e Scientifica) sia dalle le diverse necessità

di conduzione dei dottorati, dovute a svariati motivi5:

tali differenziazioni sono state discusse durante alcune

riunioni con i Coordinatori di Dottorato.

Particolare attenzione è stata posta nella valutazione

dei prodotti della ricerca, resa possibile grazie alla

presenza del Catalogo di Ateneo informatizzato, che è

stato lo strumento principe per poter creare il software

necessario. Anche in questo caso, la valutazione di tali

prodotti è stata stabilita, una prima volta e

successivamente modificata, di concerto con la

Governance dell‘Ateneo.

E‘ importante sottolineare come alcune decisioni

siano state oggetto di critiche in quanto alcuni

Coordinatori trovavano i criteri troppo stretti per le

esigenze della loro Area. Ma anche queste perplessità

sono state considerate e in parte risolte nell‘ambito

della forte collaborazione tra il Nucleo e la Governance

dell‘Ateneo.

2 Attestati dei professori di altri Atenei presso i quali si sono

recati i dottorandi, attestazione dell‘incremento delle borse

per soggiorni all‘estero, lettere di partecipazione esclusiva di

un docente italiano al dottorato, curricula dei docenti stranieri

e italiani non di Messina (per i Messinesi esiste il Catalogo di

Ateneo che è stato uno strumento indispensabile per il buon

funzionamento dell‘impianto delle schede informatizzate). 3 Si tratta di convalidare o meno le dichiarazioni che talvolta

sono inserite per inesperienza, ma che non possono dare adito

a calcoli per i punteggi degli indicatori, quali, ad esempio, le

ore impiegate nella ricerca o negli incontri con il

Coordinatore e/o i tutor per la preparazione della tesi. 4 La procedura è del tutto indipendente dalle altre, per

consentire l‘effettuazione di modifiche nei calcoli nel modo

più semplice. 5 Si pensa ai periodi di permanenza all‘estero che, in

generale, danno adito a punteggio solo se sono di almeno tre

mesi, mentre per gli scavi archeologici e la permanenza sulle

navi scendono a 1 mese.


18

Per una totale trasparenza del proprio operato, il

Nucleo ha inoltre richiesto che il software, alla

chiusura del periodo di richiesta di Rinnovi e o Nuove

Attivazioni e delle convalida amministrative6,

permettesse a tutti i Coordinatori la visione dettagliata

dei calcoli degli indicatori di tutti i Dottorati.

Si può ragionevolmente affermare che quello

dell‘Ateneo di Messina è stato, in Italia, il primo

impianto logico e software completo che ha consentito

la formalizzazione delle valutazioni sui Dottorati di

Ricerca: molte altre Università hanno, infatti, seguito

un modello molto simile. Nel Dicembre 2008 la

procedura è stata presentata nel convegno tenutosi a

Padova cui hanno partecipato tutti i Nuclei di

Valutazione. Purtroppo però, nonostante le richieste

ricevute, il nostro Ateneo non è stato in grado di fornire

tale software ad altre Università.

Un ulteriore punto a favore del lavoro svolto, è la

dedizione con cui il Prof. Mondello si è dedicato alla

valutazione della correttezza delle dichiarazioni nelle

schede ed a suggerimenti volti al miglioramento ed alla

semplificazione della procedura; per la parte operativa

sento il bisogno di ringraziare la serietà e la

professionalità del Dott. Marco Todaro e dell‘Ing.

Fabrizio De Gregori, che, con la procedura menzionata,

hanno consentito un notevole risparmio economico alla

nostra Università.

Il software si riferisce a due fasi distinte della

valutazione dei dottorati di ricerca: quella della

richiesta di Rinnovo/nuova Attivazione e quella di

Consuntivo, dove, al di là di alcune informazioni

fornite dai Coordinatori, ogni Dottorando indica il

percorso formativo svolto e il risultato delle sue

ricerche.

Come si è già detto gli indicatori sono 8, ed ognuno di

essi serve a quantificare una delle richieste ministeriali,

comprese quelle della 240, per la quale basterà

modificare soltanto il modulo di calcolo dei punteggi:

1. Numerosità del Collegio Docenti

7

2. Produttività Scientifica del Coordinatore

3. Produttività Scientifica pro capite del Collegio

Docenti

4. Accordi di collaborazione per lo svolgimento

di esperienze in un contesto di attività lavorative o per

lo svolgimento di stage in sedi di ricerca qualificate

straniere o italiane

5. Posti di dottorato aggiuntivi rispetto alle borse

finanziate dall‘Ateneo

6 Egregiamente effettuate dall‘Ufficio Dottorati che non si

potrà mai ringraziare abbastanza. 7 Il collegio docenti può essere formato solo dai docenti

indicati come tali dal MiUR.

6. Esistenza di un piano formativo formalizzato e

documentato

7. Produttività Scientifica di Ricerca pro capite

dei Dottorandi

8. Contesto Scientifico (Progetti di ricerca)

Nella tabella seguente si mostrano le differenze tra la

vecchia legislazione, quanto richiesto dalla L.240 e

l‘impianto logico, nelle schede del Nucleo, per il

calcolo degli indicatori:


8 ordinari e associati del/i settore/i concorsuali o SSD oggetto del corso, attivi in ricerca, ovvero, nei settori è opportuno, di esperti di elevata qualificazione di numero non superiore a quello dei docenti) 9 Art.5, comma 1, punto a dello Schema di decreto del MiUR ― Regolamento recante criteri generali per la disciplina del Dottorato di ricerca‖ del 27/09/2011 10 Per attivo si intende un professore che abbia pubblicato almeno tre prodotti della ricerca negli ultimi 3 anni ovvero, se dell‘aria umanistica, almeno 1 monografia. 11 Il Professore Ordinario attivo vale 1 punto, il professore associato attivo vale 0,7 punti, il ricercatore attiva vale 0,5 punti. Il Professore non attivo non da adito a punteggio. 12 I coordinatori nazionali o locali devono essere dell‘Università di Messina 13 Posti di Dottorati aggiuntivi rispetto alle borse d‘Ateneo: borse finanziate dalla comunità europea, PON, PRO, POM, Enti pubblici e/o privati, PRIN, FIRB, FSG, posti attivati con mantenimento dello stipendio

dell‘amministrazione originaria. 14 In generale il soggiorno in Italia dovrà essere di almeno 3 mesi, mentre per quelli all‘estero in sono valutati in quota parte ai 3/1 mese (v. nota 5) solo se vi sia un incremento della borsa.

Requisiti Ministeriali Precedenti Requisiti Ministeriali L. 240 Indicatore corrispondente Scheda in cui si trovano le

informazioni Valutato

la presenza nel collegio dei docenti di un congruo

numero di professori e ricercatori dell'area scientifica di riferimento del corso.

Non meno di 7 docenti per l’attivazione

Non meno di 10 per il 20% del finanziamento

Collegio docenti formato almeno da 188 professori9

attivi10

INDICATORE 1

Numerosità del Collegio Docenti11

Richiesta Rinnovo /nuova

Attivazione SI

la disponibilità di adeguate risorse finanziarie Non sono stabiliti in modo

esplicito

INDICATORE 8

Contesto Scientifico (Progetti PRIN, FIRB finanziati e/o finanziabili e Progetti

della Comunità Europea Finanziati12)


Attivazione SI

la disponibilità di specifiche strutture operative e scientifiche per il corso e per l’attività di studio e di

ricerca dei dottorandi

Non sono stabiliti in modo

esplicito Numero massimo di dottorandi compatibili con le strutture organizzative


Attivazione NO

la previsione di un coordinatore responsabile

dell’organizzazione del corso

Non cambia nulla rispetto alla

normativa precedente INDICATORE 1

Coordinatore. Non è possibile inserire una scheda senza un Coordinatore Richiesta Rinnovo /nuova

Attivazione SI

la previsione di un collegio di docenti e di tutori in

numero proporzionato ai dottorandi: non veniva

specificato però il significato di “congruo”

Collegio docenti formato almeno da 18 professori8, 9, 10

INDICATORE 1

Collegio Docenti


Attivazione SI

la previsione di un collegio di docenti e di tutori con documentata produzione scientifica nell’ultimo

quinquennio nell’area di riferimento del corso

Non cambia nulla rispetto alla normativa precedente

INDICATORE 2 e 3

Produzioni scientifiche del Coordinatore e del Collegio Docenti10 Richiesta Rinnovo /nuova

Attivazione SI

la possibilità di collaborazione con soggetti pubblici o privati, italiani o stranieri, che consenta ai dottorandi

lo svolgimento di esperienze in un contesto di attività

lavorative

Sono auspicati e se ne chiede l‘incremento, ma non vengono

fornite adeguate risorse

finanziarie.

INDICATORE 4

INDICATORE 513

Periodo formativo all‘estero

Accordi di collaborazione / convenzioni per lo svolgimento di esperienze in contesto di attività lavorative

Forme di collaborazione per lo svolgimento di esperienze in contesto di attività

lavorative non formalizzate14

Schede Consuntivo dei singoli

Dottorandi SI

la previsione di percorsi formativi orientati all'esercizio di attività di ricerca di alta qualificazione presso

università, enti pubblici o soggetti privati

Sono auspicati e se ne chiede

l‘incremento, ma non vengono

fornite adeguate risorse finanziarie.

INDICATORE 6

Programma formativo, modalità di svolgimento e finalità del corso

Obiettivi formativi orientati alla ricerca e tematiche di ricerca Indirizzi e tematiche di ricerca

Schede Consuntivo dei singoli

Dottorandi SI

l’attivazione di sistemi di valutazione relativi alla

permanenza dei requisiti di cui al presente comma

Non sono specificati meglio

neanche nella 240 INDICATORE 7

Produttività scientifica pro-capite dei dottorandi Schede Consuntivo dei singoli

Dottorandi SI

l’attivazione di sistemi di valutazione relativi alla rispondenza del corso agli obiettivi formativi di cui

all’articolo 4

Non sono specificati meglio

neanche nella 240

Modalità di valutazione periodica della preparazione dei dottorandi al fine della

prosecuzione del corso Richiesta Rinnovo /nuova

Attivazione NO

l’attivazione di sistemi di valutazione relativi alla

rispondenza del corso agli obiettivi formativi in relazione agli sbocchi professionali, al livello di

formazione dei dottorandi

Non sono specificati meglio neanche nella 240

Sbocchi professionali previsti Richiesta Rinnovo /nuova

Attivazione NO


20

Calcolo scientifico

A proposito della Ricerca Scientifica, e quindi anche

in relazione alla produttività scientifica pro-capite dei

dottorandi, è importante fare un ulteriore discorso.

Quale Responsabile dell‘Area Sistemi Informativi per

l‘Analisi dei dati d‘Ateneo e Calcolo Scientifico,

gestisco, validamente coadiuvata dall‘Ing. Sciacca e dal

Dott. Lo Re, il Settore di Calcolo Scientifico del

CECUM, mettendo a disposizione dei Ricercatori

dell‘Ateneo un insieme di risorse di calcolo piuttosto

consistente:

il cluster eneadi, costituito da sei server HP Integrity

quadriprocessori e da un server HP ProLiant

biprocessore per un totale di 26 CPU. Nello stesso rack

si trovano i server HP ProLiant che eseguono Windows

Server 2003 e consentono all‘utenza l‘uso dei

programmi MATHLAB e MATEMATICA, utilizzabili

direttamente dal portale di calcolo. Il server Xanto

(DL360), invece, insieme ai due server Voltumna

(SUNBLADE100) e Larsthurms (SUNBLADE2000)

sono utilizzati per la gestione del sito e dei software del

Settore di Supporto al Nucleo di Valutazione della

stessa area. Per quanto riguarda il dimensionamento di

queste ultime apparecchiature è necessario dire che

esse erano state acquisite per un numero di accessi

piuttosto limitato, in quanto, fino al 2007, il software a

disposizione del Nucleo di Valutazione era piuttosto

limitato. Da quando sono state sviluppate le procedure

principali delle richieste di Attivazione / Rinnovi dei

Dottorati di Ricerca e di Valutazione della Didattica

(arrivati rispettivamente alle versioni 5.0 e 2.7), il

bacino di utenza si è allargato a tutti i Coordinatori dei

Dottorati di Ricerca, ai Dottorandi per ciò che concerne

la prima procedura, ai Referenti di Facoltà, a tutti i

Docenti e gli studenti per ciò che riguarda la

Valutazione della Didattica, per un totale di oltre 2.000

utenze potenzialmente concorrenti;

Il cluster TriGrid, formato da un insieme di 28 lame

IBM LS20 e 21;

Nei due sistemi è installato il software LSF (Load

Sharing Facility) e librerie per il calcolo parallelo.

In generale l‘uso delle risorse offerte dal Settore di

Calcolo Scientifico viene effettuato da parte di un

gruppo ormai consolidato di utenti, il cosiddetto

gruppo storico, ma ad essi se ne stanno via via

aggiungendo altri che hanno iniziato a sfruttarle per le

proprie attività di ricerca o per altri progetti15

. In

15

Dal 2010 il Dipartimento di Ingegneria Civile partecipa ad

un progetto di ricerca europeo sullo sviluppo di tecnologie

sostenibili innovative per l‘energia, dal titolo

―THermoacoustic Technology for Energy Applications‖

(THATEA, http://www.thatea.eu/); il progetto è coordinato

dall‘Energy Research Centre of the Netherlands (ECN) e

quest‘ottica le risorse offerte dal Settore di Calcolo

Scientifico si sono rivelate molto significative, tenuto

conto che sul cluster ―eneadi‖, nel solo 2010, sono stati

eseguiti con successo ben 1.891 job correlati al

progetto di cui in nota, i quali hanno richiesto un tempo

totale di CPU pari a 5.703.869 secondi, corrispondenti

a 66 giorni di calcoli; il tempo medio di CPU richiesto

da questi job è stato dunque di 3.016,3 secondi, e il

valore massimo registrato è stato di 67.055 secondi.

Poiché è capitato che l‘esecuzione contemporanea di

più job eccedesse le risorse a disposizione, con la

conseguente necessità di mettere in coda uno o più job,

si è avuto un tempo totale di attesa in coda pari a ben

2.440.474 secondi, con una media di 1.290,6 secondi e

un valore massimo di 70.114 secondi, addirittura

superiore al massimo tempo di CPU impiegato dai job

del progetto.

Quanto appena detto evidenzia come, pur

limitatamente ai periodi di svolgimento dei calcoli che

riguardano determinate attività di ricerca, le risorse del

cluster ―eneadi‖ – che fino a qualche anno fa erano in

grado di soddisfare ampiamente le richieste dell‘utenza

– possano oggi rivelarsi sottodimensionate rispetto al

fabbisogno di quest‘ultima; a causa di ciò, nata

l‘esigenza di poter disporre di nuove risorse di calcolo,

si sta lavorando all‘allestimento del nuovo cluster IBM

precedentemente impiegato nell‘ambito del progetto

TriGrid.

Il cluster eneadi è formato da server che vengono

sfruttati con regolarità sia dall‘utenza scientifica che da

studenti e dottorandi di ricerca.

Nella fornitura di potenza di calcolo all'utenza va

menzionato per la sua crescente importanza il cluster

IBM (ex TriGrid). Se ne stanno rimodulando le

impostazioni (riconfigurandolo) al fine di offrire

un'equa distribuzione delle risorse, dato che tale cluster

viene già attivamente utilizzato da un gruppo di utenti.

L'alta densità di core per unità di rack disponibili, resa

possibile dall'adozione di blade IBM dotate ciascuna di

due processori Opteron dual core, consente l‘uso di un

elevato numero di core per le elaborazioni, anche di

tipo parallelo grazie all'impiego di apposite librerie.

I sistemi di calcolo scientifico messi a disposizione

del CECUM sono utilizzati anche in seguito ad una

visione allargata della ricerca. Infatti molti docenti

iniziano i loro studenti all‘uso di risorse di questo

genere nell‘ambito delle materie di cui sono titolari.

Ovviamente oltre agli studenti i due sistemi sono

pesantemente utilizzati anche dai borsisti, dai

dottorandi di ricerca, laureandi e, eventualmente, sono

stati creati account per visiting professors.

vede la partecipazione di importanti Università ed Istituzioni

di ricerca europee quali l‘Università di Manchester ed il

CNRS.

http://www.thatea.eu/


21

ON THE WAVELENGTH SHIFT BETWEEN NEAR-FIELD PEAK

INTENSITIES AND FAR-FIELD PEAK CROSS SECTIONS IN PLASMONIC

NANOSTRUCTURES

Adriano Cacciola

Dottorato di Ricerca in Fisica dell’Università di Messina

Viale F. Stagno D’Alcontres, 98166 S. Agata-Messina, Italy

e-mail: [email protected]

Abstract

The localized plasmons of metallic nanoparticles and

nanostructures display a particular behaviour: when

they are optically excited, the near-field peak

intensities occur at larger wavelengths than the far-

field peak intensities. Here we show that the magnitude

of this shift depends on the dimensions of these

nanostructures and is theoretically predictable through

an approach based on the multipole expansion of the

electromagnetic fields within the Transition Matrix

formalism. The understanding of this phenomenon is

particularly important for Surface Enhanced Raman

Spectroscopy (SERS).

Introduction

Metal nanoparticles (MNPs) have been intensively

studied within the past decade. The unique properties

of MNPs have their applications in a broad range of

different fields, including chemistry, physics, biology,

materials science, medicine, catalysis and so on [1].

These applications rely heavily on the fact that MNPs

support localized surface plasmon resonances (LSPRs),

which are excited when incident electromagnetic

radiation creates collective coherent oscillations of the

particle free electrons [2]. Such plasmon excitations

result in a large enhancement of the electromagnetic

field around the nanoparticle, yielding both a strong

absorption and scattering of light by the nanoparticle at

the plasmon resonance frequency [3]. Varying the size

and shape of metal particles we can tune the plasmon

resonances over a wide range of wavelengths [1,2,3].

Thus, understanding the properties of plasmonic

structures of different size and shape is nowadays of

primary importance for basic and applied research as

well as for modern nano-technology [1].

Although extinction, absorption, and scattering are

still the primary optical properties of interest, other

spectroscopic techniques, e.g. SERS, are sensitive to

the electromagnetic fields at or near the particle

surfaces, thus providing important new challenges for

theory.

A well known phenomenon, that has frequently been

pointed out in the literature, is that, upon optical

excitation, the maximum near field enhancements

occur at lower energies than the maximum of the

corresponding far-field quantities [4,5,6,7]. This red

shift is known to depend on the size of the particle

[8,9], with larger particles displaying a more marked

shift. A recent systematic study has provided a

phenomenological comparison of the relationship

between the near- and far-field spectra of plasmonic

particles [10], but the physical explanation of this

apparently universal behaviour of metal particles is still

controversial. Messinger et al. [4] explain this

behaviour in terms of the radial components of the

electric field which can exist only in the near-field

zone of the sphere.

Recently Zuloaga and Nordlander [11] have

explained the physical origin of this red shift through a

mechanical analogy as a general consequence of the

behaviour of damped harmonic oscillators.

In this paper we analyze the red shift effect through

an analytical and numerical approach based on the

multipole expansion of the electromagnetic fields

within the Transition Matrix (T-Matrix) formalism

[12]. We will investigate the dependence of this red

shift upon the nanoparticle size and shape. To this aim

we start our investigation with a gold sphere and

successively we extend the description to the case of

gold dimers.

Theory

We study the optical behaviour of metal

nanoparticles, both isolated or clustered, through the

multipole expansions of the electromagnetic fields

within the T-Matrix method. This is a general

approach that applies to particles of any shape and

refractive index and for any choice of the radiation

wavelength [12]. It has been successfully applied to

several research fields, e.g. for the investigation of

interstellar dust optical properties [13,14,15], in

bioastronomy [16,17], and in optical trapping

[18,19,20,21]. Expanding the incident field in a series

of vector spherical harmonics with known amplitudes

I

p

lmW , the scattered field can be expanded on the same

basis with amplitudes '

' '

p

l mA . The relation between the

amplitudes of scattered and incident field is given by


22

' '

' ' ' ' I

p p p p

l m l m lm lm

plm

A S W (1)

where '

' '

p p

l m lmS is the T-Matrix of the particle[9]. The

elements of the T-Matrix are calculated in a given

frame of reference through the inversion of the matrix

of the linear system obtained by imposing the boundary

conditions to the fields across each spherical surface

[12].

The number of subunits are limited only by the

memory demand of the computing facilities. The

calculation of the T-Matrix for a N-sphere aggregate,

requires the inversion of a matrix of order d =

2N×lM(lM +2), where lM is the l-value at which the

multipole expansion of the electromagnetic fields is

truncated [12]. The choice of the value lM is carefully

checked by convergence tests ensuring the numerical

stability of the results.

The procedure devised for the extension of the T-

Matrix formalism to the study of the optical behaviour

of an aggregate of N, not necessarily equal, spheres

whose mutual distances are so small that the interaction

effects cannot be neglected can be found in [12]. In

such case the T-Matrix approach allows to take proper

account of the multiple scattering processes among the

spheres composing the aggregate.

Results

We start our investigation with a spherical gold

nanoparticle with a radius of 100 nm. The direction of

the incident field is along the z-axis and the

polarization is along the x-axis. This configuration has

been used in all our computations.

Figure 1: Scattering cross section (thick solid

line) and NFI in the forward direction (solid

line), backward direction (dotted line), and at

90° (dashed line) respect to the incident

direction for a 100 nm gold sphere. The spectra

have been normalized to their maximum values.

In Fig. 1 we compare the normalized scattering cross

section with the normalized Near Field scattered

Intensities (NFI) for three different points located at a

distance dNF from the sphere surface given by 1/10 of

the radius. This choice for dNF has been used in all the

results that we will show. All the spectra have been

normalized to their maximum values.

As is evident from the figure, the NFI is red shifted

from the far-field spectrum. This effect appears more

clearly in the backward direction and at 90° respect to

the incident direction. In the forward direction only the

quadrupole peak appears and the red shift is much

smaller.

Along the polarization direction the quadrupole peak

almost disappears and all the energy radiated by the

particle is mainly due to the dipole contribution.

Figure 2: Scattering cross sections (solid lines)

and NFI (dotted lines) for a 30 nm gold sphere

(thin lines) and for a 50 nm gold sphere (thick

lines). The spectra have been normalized to

their maximum values.

The results shown in Fig. 2 confirm, through exact

computations performed using the T-Matrix method,

the well known red shift dependence upon the

dimensions of the nanoparticle. We performed our

computations for many different particle sizes. Here,

for the sake of simplicity, we show only the scattering

cross sections and NFI for a 30 nm gold sphere and for

a 50 nm gold sphere. As the sphere size gets smaller,

the red shift reduces as well, but never disappears.


23

In Fig. 3 we show the scattering cross section and the

NFI for a dimer made of identical gold spheres each

with a radius R=50 nm.

The dimer geometry is such that the closest distance

between the sphere surfaces is 4 nm. We computed the

NFI at the central point of the hot spot and at a distance

5 nm from the sphere surface in the external region.

We recall here that the hot spot is the region between

the spheres where the field enhancement is the highest

(see Fig. 4).

Fig. 3 clearly shows that the red shift in the hot spot

disappears, while it is still present in the dimer external

region, in analogy with the single sphere case.


line) and NFI (thin lines) at the central point of

the hot spot (solid line) and at a distance d=5

nm from the sphere surface in the external

region (dotted line) for a dimer of two identical

gold spheres (R=50 nm). The spectra have been


In Fig. 3 we show the scattering cross section and the

NFI for a dimer made of identical gold spheres each

with a radius R=50 nm. The dimer geometry is such

that the closest distance between the sphere surfaces is

4 nm. We computed the NFI at the central point of the

hot spot and at a distance 5 nm from the sphere surface

in the external region.

We recall here that the hot spot is the region between

the spheres where the field enhancement is the highest

(see Fig. 4). Fig. 3 clearly shows that the red shift in

the hot spot disappears, while it is still present in the

dimer external region, in analogy with the single

sphere case.

In order to demonstrate that the absence of the red-

shift in the hot spot is due to symmetry reasons, we

compute the scattering cross section and the NFI for a

dimer of gold spheres with different radii, R1=50 nm

and R2=100 nm. Also in this case the closest distance

between the surfaces of the two spheres is 4 nm (Fig.

5).

Figure 4: Near-field intensity enhancement map

for a silver dimer with R=75 nm. The closest

distance between the surfaces of the two

spheres is 5 nm.

These results show that, when we break the

symmetry of the dimer, the red shift appears also in the

hot spot. The effect appears both for the dipole and for

the quadrupole peak.

Conclusions

In conclusion, using the T-Matrix approach, we have

shown how the near-field spectra of plasmonic

nanoparticles are red-shifted compared to their far-field

spectra. In order to generalize the results and to provide

a systematic study of the relationship that exists

between far-field and near-field quantities, it is

necessary to extend the investigation to more complex

structures, like large aggregates of spheres.

We expect that taking into account the red shift

effect can provide improvement in understanding and

optimising surface-enhanced spectroscopies.

This physical insight into the behaviour of

plasmonic systems should be also useful for the

practical design of plasmonic nanoparticles and

nanostructures for applications of both fundamental

and technological interest.


24


line) and NFI (dashed lines) at the central point

of the hot spot region (solid line) for a dimer of

R1=100 nm and R2=50 nm gold spheres. The

closest distance between the surfaces of the two

spheres is 4 nm. The spectra have been


Acknowledgments

I wish to thank R. Saija, M.A. Iatì, F. Borghese, P.

Denti, P.G. Gucciardi, and O.M. Maragò for fruitful

discussions and support.

References [1] S. A. Maier, Plasmonics: Fundamentals and Applications,

Springer (2007);

[2] M.L. Brongersma, P.G. Kik, Surface Plasmon Nanophotonics,

Springer Series in Optical Sciences, (2007); [3] L. Novotny and B. Hecht, Principles of Nano-Optics,

Cambridge University Press, New York (2006);

[4] B. J. Messinger el al., P. Rev. B 24 (1981) 649; [5] N. K. Grady el al., P. Chem. Phys. Lett. 399 (2004) 167;

[6] A. S. Grimault el al., Appl. Phys. B: Laser Opt. 84 (2006) 111;

[7] S. Bruzzone el al., J. Phys. Chem. B 110 (2006) 11050; [8] K. L. Kelly el al., J. Phys. Chem. B 107 (2003) 668;

[9] G. W. Bryant el al., J. Nano Lett. 8 (2008) 631;

[10] B. M. Ross el al., Opt. Lett. 34 (2009) 896; [11] J. Zuloaga and P. Nordlander, Nano Letters 11 (2011) 1280;

[12] F. Borghese, P. Denti and R. Saija, Scattering from model

nonspherical particles 2nd ed., Springer, Berlin (2007); [13] M.A. Iatì et al., MNRAS 322 (2001) 749;

[14] C. Cecchi-Pestellini, A. Cacciola et al., MNRAS 408 (2010)

535. [15] M. A. Iatì, C. Cecchi Pestellini, A. Cacciola et al., JQRST 112

(2011) 1898; [16] R. Saija et al., Astrophys. J. 633 (2005) 953;

[17] A. Cacciola et al., Astrophys. J. 701 (2009) 1426;

[18] F. Borghese et al., Phys. Rev. Lett. 100 (2008) 163903; [19] R. Saija, et al., Opt. Exp. 17 (2009) 10231;

[20] E. Messina, E. Cavallaro, A. Cacciola et al., ACS Nano 5

(2011) 905; [21] E. Messina, E. Cavallaro, A. Cacciola et al., J. Phys. Chem. C

115 (2011) 5115.


25

MASS QUADRUPOLE SPECTROMETRY APPLIED TO LASER-

PRODUCED PLASMAS AND MICROWAVE IGNITED PLASMAS

F. Di Bartoloa, *, L. Torrisi

b,c, S. Gammino

c , F. Caridi

d, D. Mascali

c,e, G. Castro

c,f , L. Celona

c,

R. Miracolic,f

, D. Lanaiac, R. Di Giugno

c,f.

a) Dottorato in Fisica dell’Università di Messina, Dip.to di Fisica, V.le F. Stagno D’Alcontres 31, 98166, S. Agata-

Messina, Italy

b) Università degli Studi di Messina, Dip.to di Fisica, V.le F. Stagno D’Alcontres 31, 98166, S.Agata-Messina, Italy

c) INFN - Laboratori Nazionali del Sud, via S.Sofia 62, 95123 ,Catania, Italy

d) Università degli Studi di Messina, Facoltà di Scienze MM.FF.NN., V.le F. Stagno D’Alcontres 31, 98166, S. Agata-

Messina, Italy

e) CSFNSM, Viale A. Doria 6, 95125 Catania, Italy

f) Università degli Studi di Catania, Dipartimento di Fisica e Astronomia, V. S.Sofia 64, 95123 Catania, Italy

* Corresponding author, e-mail: [email protected]

Abstract

The mass quadrupole spectrometry (MQS) permits

the characterization of non-equilibrium and

equilibrium plasmas obtained by means of laser

ablation and microwave ionization. A Nd:Yag laser,

150 mJ pulse energy, 3 ns pulse duration, operating at

1064 nm fundamental and 532 nm second harmonic

wavelength, at intensities of the order of 1010 W/cm2,

in single pulse or at a repetition rate between 1 and 10

Hz, interacting with solid targets placed in high

vacuum produces ablation with plasma formation. It is

possible to analyze the ion and the neutral emission

from plasma in the mass range 1-300 amu with a mass

resolution better than 1 amu and a sensitivity of the

order of 1 p.p.m.. Moreover, it is possible to select the

ion energy in the range 1 eV – 1 KeV with an electric

deflection filter.

MQS allows to measure the temperature and density

of the plasma, the relative ion and neutral amounts, the

fractional ionization of the plasma, the elements and

chemical compounds of the species participant to the

plasma formation, the ion charge state, the ion energy

distributions and the angular distribution of the emitted

ions. Operating in repetition rate it measures the depth

profile of peculiar elements in the ablated targets.

Moreover, MQS permits also to characterize

microwave ignited plasmas, obtained by means of

microwaves at two different frequencies, 2.45 GHz

(Magnetron) and 3.7478 GHz (TWT), axially launched

inside the plasma chamber, where a strongly non

uniform magnetostatic field exists (with a maximum

value of 0.1 T), with two possible configurations

depending on the used ion source (Plasma Reactor or

VIS). In the regions under ECR (Electron Cyclotron

Resonance) the X-B conversion is possible, the

incoming electromagnetic extraordinary mode X is

converted into a Bernstein wave B, i.e. an electrostatic

wave which can propagate in an overdense plasma.

Plasma density and temperature measurements,

obtained with a Langmuir Probe and X-ray detectors,

confirmed successfully the mode conversion and the

formation of an overdense plasma.

The similarities with non-equilibrium plasmas

generated by laser ablation will be described along

with the differences.

Keywords: Mass Quadrupole Spectrometry, Laser-

Plasma, Electrostatic Bernstein Waves, Plasma heating,

Plasma vortex

Introduction

Mass spectrometry (MS) is an analytical technique to

measure the mass-to-charge ratio of charged particles

(m/q).

A mass spectrometer is used to determine elemental

composition, compounds and isotopes and, if there is

also an energy filter, ion and neutral energy

distributions. It permits to analyze both ions and

neutrals, and is made up of three main parts: an internal

ionization source, a mass analyzer and a detector [1].

It is known that intense pulsed laser beams, with an

intensity of 1010

W/cm2, can be focused on a solid

material to produce ablation and formation of hot non-

equilibrium plasmas, which have a duration of a few

nanoseconds. The processes developed inside the laser-

generated plasma depend on many parameters, such as

the laser characteristics, lens focalization, target

composition, irradiation conditions, etc..

PLA obtained with ns lasers at high intensity

generates hot plasma at the target surface, which

expands in vacuum at supersonic velocity mainly along

the normal to the irradiated target surface. A plasma

characterization, in terms of temperature, density,

energy of ejected particles, fractional ionization and

charge state distribution, necessary to differentiate the

plasma laser production, can be obtained.

mailto:[email protected]


26

Equilibrium plasmas are generated by means a

Microwave Discharge Ion Source (MDIS), usually

used to produce high intensity proton beams (above 50

mA). The operations of these devices is essentially

based on the so called off-resonance discharge in a

quasi-constant magnetic field B~0.1 T, obtained by

launching microwaves with f= 2.45 GHz or 3.7478

GHz inside a metallic cavity of few cm of length and

diameter. Such devices are density limited if the ECR

is the only heating mechanism: the electromagnetic

waves cannot propagate over a certain density, called

cut-off density. To overcome the density limitations

electrostatic Bernstein waves (EBW) heating [2] is an

option. The EBWs are able to propagate in largely

overdense plasmas, i.e. plasmas above the cut-off (ncut-

off=3x1010

cm-3

), being absorbed at cyclotron harmonics

[3]. EBW are created inside the plasma when a X

wave, i.e. an extraordinary, E.M. wave, is converted

from an E.M wave. It can be shown that X waves

convert into EBW and ion waves at Upper Hybrid

Resonance, when 2 2RF P C P being the

plasma frequency and 2C being the cyclotronic

frequency.

Material and methods

A Q-switched Nd:Yag pulsed laser operating at 1064

nm fundamental wavelength and at 532 nm second-

harmonic wavelength, with 3 ns pulse duration and 160

mJ maximum pulse energy, in single shot and

repetition rate (1 and 10 Hz) mode, was employed for

the measurements.

The laser beam was focused, through a 50 cm focal

lens placed in air, on the surface of a SiO2 target, on

which it produces a 0.5 mm2 spot size, the laser-target

interaction occurs inside a vacuum chamber, at 5 x 10-6

mbar pressure, and leads to the plasma formation. Ions

and neutral particles are analysed by the MQS.

Two types of mass quadrupole spectrometer have

been employed:

1) a classical version of MQS, a Pfeiffer Vacuum

Prisma Plus QMG 220, Mass Range 1-300 amu, Mass

resolution < 0.3 %, Sensitivity (SEM) 1 ppm;

2) a special electrostatic mass quadrupole

spectrometer with an energy filter, Hiden EQP 300,

Mass range 1-300 amu, energy range 1 eV-1 keV,

Sensitivity 1 ppm.

The second type of mass spectrometer, differently

with respect a classical MQS, permits to plot the

energy distribution of neutral and charged species in

the energy range 1 eV – 1 keV. Figure 1 shows the

experimental set-up (a) and the scheme of the Hiden

EQP instrument (b). EQP is placed at 45º with respect

to the incidence laser beam, i.e. along the normal to the

target surface [4].

We also used Cu, Al and Ta targets for our

measurements.

EQP spectra were analysed in order to determine the

Cu ion energy distribution and separate the neutral

component from the ionic component for Al and Ta

targets. The fits of the experimental energy

distributions were performed by means the ‗‗Peakfit‖

numerical code using the ―Coulomb-Boltzmann

shifted‖ function:

(0.)

3

2

1( )

2 ( )

1exp ( )k C

Af E E

m kT

E E EkT

(1)

Fig.1 Scheme of the EQP instrument (a) and

photo of the experimental set-up (b)

Vacuum chamber

Laser system

MQS

b)

a)


27

The characterization of equilibrium plasmas has

been done by means a MDIS called VIS (Versatile Ion

Source). The source body consists of a water-cooled

copper plasma chamber (100 mm long and 90 mm

diameter). VIS enable us to have purely off-resonance

microwave injection (which is not possible using

Plasma Reactor, another MDIS with a slightly different

magnetic profile). Microwaves have been generated by

using a conventional 300 W magnetron, able to

generate 2.45 GHz microwaves, or a Travelling Wave

Tube (TWT), able the generate microwaves from 3.2 to

4.9 GHz. The typical working frequency when using

TWT was 3.7478 GHz. The measurements of

temperature and plasma density have been carried out

by using a movable Langmuir probe (LP). A Si-Pin X-

ray detector has been used for the measurement of X

rays spectra in different plasma conditions. The

detector is able to detect X rays with energy greater

than about 1 keV.

Results and discussions

A. PLASMA LASER ABLATION (PLA)

MQS can operate versus mass and versus time. In

the first case we have a mass spectrum, where each of

the detected peaks corresponds to a certain element or

chemical compound. In the second case we obtain a

MQS time spectrum, for some selected masses, which

allows to know the relative elemental concentrations

vs. the ablation time, permitting to plot the element

depth profiles. The mass quadrupole spectrometer

must be calibrated to know the exact number of atoms

or molecules of the target detected during the laser

ablation. In Figure 2 (a) the apparatus for the MQS

calibration is shown [5,6]. In our calibration test, we

employed a mixture of gas (50% Helium and 50%

Argon) enclosed in a volume V0 = 55.8 cm3. The initial

and final pressure of the gas in this volume are Pi and

Pf, respectively, at a room temperature T = 22ºC.

After that we open the Valve 3 in order to introduce

a known gas quantity in the vacuum chamber, very

near to the target position. We introduce a molecular

number N = 0.668 x 1020

of Argon and Helium atoms

into the vacuum chamber.

The calibration spectrum obtained by using the MQS

permits to calculate the yield of Ar corresponding to 84

C. Afterwards we obtain the target spectrum which

permitted us to calculate the yield of Si corresponding

to 0.04 C. Calculating the ablation yield is possible by

means the following proportion

: Ar = Y : Ar SiY atoms X atoms Si

(2)

Fig.2 Scheme of the gas calibration apparatus.

Thus the ablation yield resulted 3.18 x 1016

atoms of

Si ablated for laser pulse.

EQP Mass Spectrometer permits to obtain the ion

energy distribution for a Cu target at two different laser

energies, 40 mJ and 160 mJ, respectively. In the first

spectrum the peak energy is 3eV while in the second

one the peak energy is 17 eV. In figure 3 spectra

obtained at energy of 160 mJ are shown.

Making a fit with a ―Coulomb-Boltzmann shifted‖

function we can know two important parameters of a

plasma, the temperature KT and the acceleration

voltage V0. The temperature is 2.9 eV and 8.9 eV,

respectively.


28

Fig. 3 Ion energy distribution and fit for a Cu

target at a laser energy of 160 mJ.

Assuming the peak energy to be representative of the

distribution mean energy, we find that the mean energy

for the only ions is higher with respect to the spectrum

obtained detecting ions plus neutrals. At 150 mJ the

neutral plus ion mean energy is 85 eV and 115 eV for

Al and Ta, respectively. At 150 mJ the only ion mean

energy is 95 eV and 120 eV for the two cases,

respectively. Thus ions have mean energy higher with

respect to neutral specie.

The ‗‗Peakfit‖ deconvolution process applied to the

ions plus neutral spectra separates the two components,

ions from neutrals, and permits to extrapolate the

neutral energy distribution by the difference between

the ions plus neutral spectrum and the only ion

spectrum. Fig. 4 shows the deconvolution spectrum

obtained from an aluminium target. Deconvolution

spectra report the neutral energy distribution

(continuum line) obtained subtracting the only ion

spectrum (full dots) to the ion plus neutral spectrum

(open dots). The energy distributions of the neutral

specie, obtained irradiating at 150 mJ pulse energy,

show mean energies, E , of about 60 eV and 65 eV for

Al and Ta ablation, respectively. These energies are

representative of the plasma temperature through the

following relationship:

( ) 2 ( ) / 3kT eV E eV (3)

where k is the Boltzmann constant. Eq. (2) gives 40

eV and 43.3 eV for Al and Ta neutral temperature,

respectively.

Ions are characterized by energy higher with respect

to the neutrals, due not only to the thermal interactions

between the plasma particles and to the adiabatic gas

expansion in vacuum but also to the Coulomb

interactions between the charged species. [7]

Fig.3 Ion energy distribution and fit for a Cu target at

a laser energy of 160 mJ.

B. PLASMAS MICROWAVES-GENERATED

In the measurements performed with plasmas in

equilibrium, we modified the position of the magnetic

field with respect to the plasma chamber of VIS; in

such a way, microwave injection takes place at

different values of magnetic field. In figure 5 are

shown. We use as reference BECR. X ray were detected

particularly in position D (Binj/BECR=0.92, 1 keV

spectral temperature). When the injection approaches

Fig.4 Deconvolution spectrum reporting the

neutral energy distribution (line) obtained

subtracting to the only ion spectrum (fill dots)

the ion plus neutral spectrum (open dots) for Al

ablation.

BECR, X rays tend to disappear and finally, at

position A (Binj/BECR>1), no X rays were detected.

These results show that the production of high energy

X rays (T>1 keV) takes place only in case of under-

resonance discharge, that is the required condition to

have UHR placed somewhere inside the plasma.

Emittance measurements carried out in configuration A

and in configuration D have shown a larger emittance

in configuration D (0.207 πmm mrad) than in

configuration A (only 0.125 πmm mrad). The

emittance depends by the magnetic field at

A


29

extraction Bext, the radius of extraction r , the ratio of

ion mass in amu to charge state of the ion beam M/Q

and the root square of ionic temperature [8,9].

2 10.016 0.032

/ /

iext

kTr r B

M Q M Q (4)

In our magnetic configurations emittance only

depends on iT . Ionic waves are absorbed by ions

through Landau damping. If Ti are high we have a

large emittance, therefore the more intense beam

permitted by EBWs will be balanced and the

brightness, that is the current intensity-emittance ratio,

will not change and the ion source will not efficient. If

Ti are low we have an high current intensity, due to

high density possible with EBWs, a low emittance and

therefore an high brightness: the ion source will be

efficient. However if Ti are very high, in fact, value of

10 keV are possible due to the generation of vortex

inside the plasma, we will get auto-accelerated ions,

considering that in a common ion source ions have

energy of eV or a fraction of eV [10].

Conclusions

The mass quadrupole analyser measures the mass-to-

charge ratio (m/z) of the ions produced.

A mass quadrupole spectrometer allows to determine

main plasma parameters as the plasma temperature

(KT), density (n), fractional ionization (f=ni/nt),

acceleration voltage (V0) and electric field (E) [10].

EQP demonstrated high versatility to investigate on the

amount and energy distribution of neutrals and allows

to measure the plasma temperature starting directly

from the neutral energy distribution. We will be

performing measurements with the Mass Quadrupole

Spectrometer Hiden EQP 300 to determine ions energy

inside an equilibrium plasma in which a EBWs-heating

mechanism occurs. In such a way we will compare ions

energy obtained in non-equilibrium plasmas with that

ones obtained in equilibrium plasmas to understand if

EBW-heating mechanism allows to have an efficient

ion source or high-energy autoaccelerated ions.

Fig. 5 Position of Microwave injection with

respect to off-resonance, in configuration B, C

and D the injection occurs under-resonance (a);

X ray detected at different position of magnetic

field (b).

References [1] E. De Hoffmann and V. Stroobant, Mass Spectrometry: Principles and

Applications, 3rd ed.Wiley (2007). [2] Ira B. Bernstein., Phys. Rev.,

109, (1958) 10;

[2] Ira B. Bernstein., Phys. Rev., 109, (1958) 10;

[3] K. S. Golovanivsky et al., Phys. Rev. E 52, (1995) 2969;

[4] L. Torrisi et al., NIM B266 (2008) 308;

[5] L Torrisi. et al. Rad. Eff. and Def. in Solids, 161(1) (2006) 3-13.

[6] F. Di Bartolo et al. Nucleonika (2011), submitted

[7] L . Torrisi et al. , Appl. Surf. Sc., 252 (2006) 6383;

[8] D. Mascali et al., NIM A, 653 (2011) 11;

[9] G. Castro et al., ICIS ‘11, Rev. Sc. Instr., (2011), in press;

[10] K. Nagaoka et al., Phys. Rev. Lett.89 (1992) 7.

-20 -10 0 10 20700

800

900

1000

1100

1200

Position [mm]

B [G

]

Magnetic field [G]

ECR = 875 G

D C B A

a)

b)


30


31

FUSION REACTIONS IN COLLISIONS INDUCED BY LI ISOTOPES ON SN

TARGETS

M. Fisichellaa,b

, A. Di Pietrob, A. Shotter

c,d, P. Figuera

b, M. Lattuada

b,e, C.Marchetta

b, A.Musumarra

b,e, M.G.

Pellegritib,e

, C.Ruizc, V. Scuderi

b,e, E.Strano

b,e, D.Torresi

b,e, M.Zadro

f

a)Dipartimento di Fisica, Università di Messina, Messina, Italy

b)INFN- Laboratori Nazionali del Sud and sezione di Catania, Catania, Italy

c)TRIUMF, Vancouver, Canada

d)School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK

e)Dipartimento di Fisica ed Astronomia, Università di Catania, Catania, Italy

f)Ruđer Boŝković Institute, Zagreb, Croatia

Abstract

For investigating the role of the Q-value for neutron

reaction in fusion reaction induced by weakly bound

nuclei, fusion reactions of lithium isotopes with a

combination of different Sn isotopes have been proposed,

by using an activation technique. 6Li+

120Sn and

7Li+

119Sn

have been already performed. I will show here the result

of the preliminary analysis of these two reactions.

Introduction

Recently more and more experimental evidences have

been observed concerning the enhancement of the sub-

barrier fusion cross section due to neutron transfer, both

in reaction with stable nuclei [1,2] and especially in

reaction with weakly bound nuclei[3]. In particular the

enhancement seems to be related to sign of the Q-value

for neutron transfer. A new mechanism has been proposed

[4] for the sub-barrier fusion of weakly bound nuclei, in

which an intermediate rearrangement of valence neutrons

with positive Q-value may lead to a gain in kinetic energy

of the colliding nuclei and, thus, to enhancement of the

barrier penetrability and therefore of the fusion cross-

section. To investigate the role played by the coupling to

transfer channels having positive Q-value, we have

proposed to study the fusion of lithium isotopes with a

combination of different Sn isotopes. The systems which

would like to study are 6Li+

120Sn,

7Li+

119Sn,

8Li+

118Sn

and 9Li+

117Sn. All these reactions lead to the same

compound nucleus but are characterized by different Q-

value for neutron transfer. The fusion cross section are

measured by using an activation technique where the

radioactive evaporation residues produced in the reaction

are identified by the X-ray emission which follows their

electron capture decay.

The 6Li+

120Sn,

7Li+

119Sn have been already performed at

LNS, Catania. The 8Li+

118Sn,

9Li+

117Sn will be performed

at TRIUMF, Canada.

Experimental technique

As in our previous experiment [5,6], we proposed to

measure the fusion excitation function by using an

activation technique, based on the off-line measurement

of the atomic X-ray emission following the electron

capture decay of the evaporation residues produced in the

reactions.

The direct detection of E.R., produced in the collision of a

low energy light projectile onto a medium target is not

possible since the largest fraction of E.R. produced will

not come out from the target owing to the their low

kinetic energy. But by choosing a suitable target, with the

help of statistical model calculation, it is possible to

obtain E.R. unstable against E.C. decay and so it is

possible to identify the E.R. by looking at their X rays.

This technique consists of two steps: the activation of the

target and the off-line X-ray measurement.

The activation step of the measure has been performed in

the CT2000 scattering chamber at LNS with the 6Li and

7Li beams delivered by the SMP Tandem Van Graaff

accelerator. A stack of four Sn targets followed by Nb

catchers were irradiated with the Li beam. The catchers

were needed in order to stop the residues emerging from

the previous target and to slow down the beam, thus

increasing the average difference in beam energy for the

different targets. Possible reactions induced by the beam

on the 93

Nb catchers do not represent a problem since the

X-ray energies are different to the ones corresponding to

reactions on 64

Zn. By activating a stack of targets it is

possible to extract the cross section at different energies

without changing the beam energy thus reducing the

beam time needed to perform an excitation function

measurement with the very low intensity radioactive

beams. This technique is for this reason very useful in the

case of radioactive beam.

Two irradiation runs are been performed for each system:

1) A first stack was irradiated with 25 MeV 6,7

Li beam

of about 1010

pps for about three hours.

2) A second stack was irradiated for about three days

(to optimize the 124

I production at low energy) with 21

MeV 6,7

Li beam.

By using these stacks, a centre of mass energy range

between 16 MeV< Ec.m. < 24 MeV .To extract the

production cross section it is necessary to measure the

beam current as a function of time for the entire duration

of the activation step. This operation has been performed

using two Surface Barrier Silicon Detector collecting the

particles scattered by a thin gold foil placed before the


32

stack on the beam line. Since the scattering is of

Rutherford type, the beam intensity can be extracted by

his well-known cross-section formula. With the two

symmetrical monitors it is possible to reduce systematic

errors due to mechanical misalignments. After the

irradiation, the E.R. emitted from the different targets

(together with the corresponding catcher) were measured

off-line using Pb shielded large area Si(Li) detectors.

Each measurement was repeated in order to measure the

activity as a function of time. For determining the fusion

cross section it is really important to know the intrinsic

efficiency of the detector. We measured the efficiency of

our detector using some calibrated sources, because in the

energy range, in which we are interested in, the efficiency

for these detector is strongly dependent from the energy.

PRELIMINARY RESULTS

Typical X-ray spectra measured off-line for the reaction 6Li+

120Sn is shown in figure 1, where the peaks

corresponding to Kα and Kβ X-ray emission of Sb and I

are shown. The Kβ emission represents about 15% of the

total k X-rays emission. In the present experiment, the

analysis was performed only on the Kα lines.

Figure 1 Typical X-ray spectra measured off-line

for the reaction 6Li+

120 Sn at 25 MeV. It is possible

to distinguish Sb and I peaks.

From the X-ray energies we can only identify different

elements but not different isotopes. We can characterize

the isotope by following the time behavior of the X-ray

lines, characteristic of each element, and by fitting it

using the known half-lives. Plotting these data on a semi-

logarithm graph (that is ln A vs t) should give a straight

line of slope -λ, the decay constant .In figure 2 a typical

activation curve for the reaction 6Li+

120 Sn at 25 MeV is

shown. It is possible to observed three different slope

which characterize this curve. Each slope correspond to a

different I isotope produced in the reactions. In particular

one may observe the contribution of 123,124,125

I.

Figure 2 Activity curve for the I isotopes, obtained

for the reaction 6Li+

120 Sn at 25 MeV.

By fitting the activation curves for each E.R. one

obtains the A0exp, that is its activity at the end of the

irradiation time, which is another important quantity for

the measurement of the fusion cross section.

Future perspectives

The fusion cross section is given by the following

relation:

0exp

0i t T

A

N N K (1)

where 0exp 0A represent the number of compound

nuclei at the end of the irradiation time. As it was told

before, 0expA is obtained from the fit of the activation

curve (figure 2).

The term is then corrected for the fluorescence

probability ( K ) and for the detector efficiency ( T ),

which is determined experimentally by using calibrated

sources. tN is the number of target atom per cm2 and tN

is the incident beam current (i.e. the number of incident

particles), which is determined by analyzing the

Rutheford scattering data. The next step of my analysis

will be just the determination of iN , and then the

measurement of the fusion cross section for the two

reaction already performed. From the comparison of the

fusion cross sections of all the systems it will be possible

to investigate on the possible role of the Q-value for

neutron transfer in the fusion reaction.

References

[1] Trotta et al., Phys.Rev. C 65, 011601(2002);

[2] Stefanini et al, Phys.Rev. C 74 034606 (2006);

[3] Penionzhkevich et al., Phys. Rev. Lett. 96 162701(2006);

[4] Zagrebaev et al., Phys. Rev. C 67 061601(R) (2003);

[5] Di Pietro et al. Phys.Rev.C 69 (2004) 044613;

[6] Di Pietro et al. Europhys.Lett. 64 (2003) 309.


33

PARTICLE CORRELATIONS AT INTERMEDIATE ENERGIES AND THE

FARCOS PROJECT

T. Minniti1,2

and Farcos/Chimera collaboration

1Dipart. di Fisica, Università di Messina, v.le F. D’Alcontres 31, 98166 S. Agata, Messina, Italy.

2INFN-Gruppo collegato di Messina, Messina, Italy.

Corresponding Author: [email protected]

Keywords: Particle correlations, correlation functions.

Abstract

The study of correlations between two or more

particles emitted during a nuclear reaction provides

tools to explore the space-time properties of the

reaction and spectroscopic features of produced exotic

clusters [1]. Correlation imaging techniques are known

to provide ―space-time‖ snapshots of particle emitting

sources [1]. These sources allow one to extract the size

of emission regions in properties of nuclear matter

produced during the reaction. Moreover, two-nucleon

correlations probe the relative emission times of pre-

equilibrium protons and neutrons that are strongly

affected by the symmetry energy and its symmetry

dependence [2]. Studies with particle correlators used

in heavy-ion collision experiments conducted at MSU

and at the LNS will be presented and discussed. Future

improvements of these studies require a new array of

telescopes with high angular and energy resolution

coupled to a 4 detector necessary to perform better

exclusive measurements. In order to address these

topics a new project has been started at the INFN,

Sezione di Catania and Laboratori Nazionali del Sud.

The name of this project is FARCOS (Femtoscope

ARray for COrrelations and Spectroscopy) and it

consists of building an array of double-side silicon strip

detectors and CsI(Tl) crystals characterized by high

angular and energy resolution. Farcos will represent an

important scientific upgrade of the physics studies with

the Chimera detector at INFN. The array can be used

as a correlator to be coupled to existing 4 detectors

such as Chimera at LNS. Such as 4 device is

necessary to characterize the collision events

(determination of impact parameter, reaction plane,

fragment yields and spectra) while Farcos is used in

coincidence to measure correlation functions. The

Farcos array will be characterized by a compact

electronics and a geometric flexibility that will also

allow it to be transported to different laboratories,

depending of the beam/target combination to be

studied, that to be adapted to different 4 detector

environments (Chimera at the LNS, Indra at GANIL,

etc.). These features and their impact in future

programs of Farcos+Chimera experiments at the LNS

of Catania will be described. These will involve

experiments to study decay channels of unbound and

exotic nuclei produced in both direct reactions with

radioactive beams and with heavy-ion collisions at the

LNS of Catania [3,4]. In the second case, several

unbound states are indeed produced during the

dynamical evolution of heavy-ion collisions and one

can study some spectroscopic properties such as their

sequential decays proceeding through the production of

sequences of unbound nuclei or cluster and nuclear

molecular states [4].

Introduction

The study of correlations between particles emitted

during a collision between two heavy ions provides

information about the space-time properties and

quantitative understanding of reaction dynamics. This

in turn depends on the details of the nuclear interaction

and the equation of state (EoS) of nuclear matter. The

future radioactive beam facilities as well as the existing

stable beam laboratories will allow studying these

problems with higher sensitivity to the isospin degree

of freedom thanks to the capability of accelerating

highly N/Z asymmetric beams at intermediate energies.

In this respect, detectors capable of detecting all

reaction products on an event-by-event basis and

measure their reciprocal correlations are mandatory

[1,2]. Different observables need to be measured over a

large solid angle coverage with high energy and

angular resolution. The solid angle coverage

guarantees a characterization of the collision event.

The energy and angle resolution are important in order

to measure the momentum vectors and kinetic energies

of the detected particles and explore their correlations.

Recent implementation of pulse-shape identification

techniques promise to provide unique capabilities [3-5]

that will allow studying nuclear dynamics even at low

energies at facilities such as Spiral2 and Spes [6].

In this contribution we present the physics cases for

the construction of a detector array meant to measure

correlations between particles and fragments in

coincidence with large solid angle arrays. The name of

the project is Farcos, standing for Femtoscope ARray

for Correlations and Spectroscopy. It is expected to

address topics in ―femtoscopy‖ via intensity

interferometry and spectroscopy with radioactive

beams.


34

Dynamics and two-particle correlations

Heavy-ion collisions allow one to explore the

properties of nuclear matter under extreme conditions.

A clear understanding of the dynamics of heavy-ion

collisions is required. Particles are emitted at different

stages that are difficult to isolate. It is therefore

important to disentangle particle and fragment emitting

sources. Where and when are fragments produced?

Understanding dynamics in heavy-ion collisions

requires tracing-back particle and fragment emitting

sources. Such challenge can be accomplished by using

two-particle correlation function known to be sensitive

to the space-time features of nuclear reaction

mechanisms [7]. The shape of correlation functions

probe important transport properties of nuclear matter

and the density dependence of symmetry energy in the

equation of state.

Figure 1. Left panel: Two-proton correlation

functions measured in Ne+Au collisions at

E/A=75 MeV. See Ref. [8] for details. Right

panel: emitting source functions extracted by

imaging.

Two-proton correlation functions, 1 ( )R q , is

defined as the ratio between the two-proton

coincidence and uncorrelated spectra, ( )coinY q and

( )uncoY q , respectively. q is the relative momentum

between two protons in coinY and uncoY spectra.

Uncorrelated proton pairs are usually constructed by

coupling protons from different events. Fig. 1 shows

such a correlation function in the case of N+Au

collisions at E/A=75 MeV [8]. The peak at q=20

MeV/c is due to the nuclear interaction between the

two protons and determines the spatial extent of the

emitting source, S(r), defined as the probability of

emitting two protons with a relative distance r recorded

at the time when the second proton is emitted. Imaging

techniques [8 and Refs. therein] have been successfully

used to extract the emitting source function from the

measured correlation function. This images represent

sort of ―space-time pictures‖ of the emission [7-9]. The

right panel of Fig. 1 shows the source functions, S(r),

extracted from the correlations represented on the left

panel. The source function not only provides

information about the size/volume of the emitting

source, but also allows us to estimate the relative

contributions between fast dynamical pre-equilibrium

sources and slowly evaporating sources characterizing

the later thermalized stages of the reaction [8]. This

sensitivity of R(q) to the space-time features of the

reaction becomes very useful as tool to explore

transport properties of nuclear matter. Indeed

microscopic transport models have shown sensitivity to

the nucleon-nucleon (NN) collision cross section in the

nuclear medium [9] and to the density dependence of

the symmetry energy [10]. Such research program

requires also the difficult task of measuring p-p, n-p

and n-n correlation functions in the same experiment

[10]. Coupling charged particle and neutron detectors

is also a priority in this respect.

Extending these measurements to fragment-fragment

correlation functions allows one to extract space-time

information about the stage of heavy-ion collisions

when nuclear matter at low density breaks-up into

complex fragments possibly indicating the occurrence

of a phase-transition [11] and carrying important

signatures of the effects of the symmetry energy and its

density dependence. The possibility of measuring

fragment correlation functions is further enriched by

the introduction of powerful pulse-shape capabilities

that would allow identifying fragments at low kinetic

energies [3,4]. These fragments can be identified only

by a detailed study of the shape of the signal induced

by their passage through the detector [2-4]. Another

important application of intensity interferometry is

represented by the study of correlations between unlike

light particles, such as proton-alpha, deuteron-alpha,

deuteron-3He, etc. [7]. An extended study of all these

correlation functions would allow a reconstruction of

several emitting sources in the same reaction. These

light particle correlations are usually characterized by

the presence of several resonances and a precise

measurement of their position and shape is mandatory

in order to probe their emitting sources. High angular

resolution is thus a key feature of an array meant to

perform correlation measurements between light

particles.

Correlation functions as a spectroscopic tool

During the dynamical evolution of the system

several loosely bound nuclear species are produced for

a very short time and decay. Their unstable states can

be identified and explored by detecting all the products

of their decay in coincidence. A typical example of this

type of analyses has been shown in Ref. [12] where p-7Be correlation functions were measured in order to

study unbound states in 8B nuclei and probe their spins


35

[12]. In a more recent experiment, three- and four-

particle correlation functions have been used to study

highly lying unbound states in 12

C and 10

C nuclei [13].

Three-alpha particle correlation functions can be used

to study the decay of internal states in 12

C. While two-

alpha-two-proton correlation functions probe 10

C

decay. In the case of 12

C these correlation studies allow

one to disentangle the direct decay into three alpha

particles from the sequential decay into 8Be+alpha with

a subsequent decay of 8Be into two alphas. In the case

of 10

C studies one can identify the decay sequence of

unbound states that produce intermediate states in 6Be,

8Be and

9B [13]. The techniques reported on Ref. [13]

show that one single heavy-ion collision can provide

access to some spectroscopic information of exotic

unbound states. The availability of very proton-rich

beams at the future exotic beam facilities can enhance

the possibility of producing even more exotic

resonances and study their decay properties.

Figure 2. Left panel: Schematic view of the

expected design of Farcos telescopes. Right

panel: Coupling of the Farcos array to the

Chimera detector at the LNS of Catania.

Required array features

Based on the physics cases outlined above, we plan

to build an array of silicon strip and CsI(Tl) telescopes

to be coupled to large detector arrays such as

Chimera@LNS-Catania. A minimum of about 15

telescopes is required in order to address a number of

physics cases as outlined above. However a larger solid

angle coverage would significantly increase the

scientific reach of the project. The array will have a

large geometric flexibility. Silicon strip detectors with

thicknesses of 300 and 1500 m (6.4 x 6.4 cm2) will be

followed by 6 cm –long CsI(Tl) crystals arranged in a

square configuration 2 x 2 (each crystal will have a

front face of 3.2 x 3.2 cm2). This array will provide an

angular resolution up to about 0.1o at a distance of 1 m

from the target. The left-end side of Fig. 2 shows a

schematic view of the basic telescope. The geometry

flexibility of the telescopes is expected to allow the use

of an additional silicon strip detector aimed at lowering

the identification threshold. Low thresholds will also

be attained with pulse-shaping techniques [3-5].

Silicon nTD solutions are also under consideration to

improve pulse-shaping capabilities. The required

electronics will need to address the goal of obtaining

high resolution, high dynamic ranges and high

flexibility (programmability) in order to identify light

and heavy fragments. Due to the large number of

channels that will be employed in the array, an

integrated electronics solution will be required. The

right-end side of Fig. 2 shows a possible arrangement

of the array inside the Chimera reaction chamber at the

LNS of Catania. The use of the array in studying

correlations between charged particles and neutrons is

also envisioned and will require a specific study on the

materials required in order to couple Farcos telescopes

to neutron counters.

The high flexibility of the array will certainly allow

further applications at the future radioactive beam

facilities, especially when studying reactions induced

by proton-rich beams. These beams will allow studying

correlations between charged particles emitted by

short-lived exotic nuclei abundantly produced close to

the proton-drip line (two- and multi-proton emitters,

etc.). Also, studying direct reactions induced by

radioactive beams, such as (p,d), (d,p) etc. reactions,

will be possible due to the envisioned high energy and

angular resolution and to the geometric flexibility [14].

References 1. J. Pouthas et al., Nucl. Instr. and Meth. A 357 (1995) 418;

2. A. Pagano et al., Nucl. Phys. A681 (2001) 331c; 3. A. Alderighi et al., IEEE Trans. on Nucl. Sci. 52, (2005) 1624;

4. L. Bardelli et al., Nucl. Instr. Meth. A 605 (2009) 353;

5. L. S. Barlini et al., Nucl. Instr. Meth. A 600 (2009) 644; 6. http://www.ganil-spiral2.eu; http://www.lnl.infn.it/~spesweb;

7. G. Verde et al., Eur. Phys. J. A 30 (2006) 81; 8. G. Verde et al., Phys. Rev. C 65, 054609 (2002);

9. G. Verde et al., Phys. Rev. C 67, 034606 (2003);

10. L.W. Chen et al., Phys. Rev. Lett. 90, 162701 (2003); 11. L. Beaulieu et al., Phys. Rev. Lett. 84, 5791 (2000);

12. W.P. Tan et al., Phys. Rev. C 69, 061304 (2004);

13. F. Grenier et al., Nucl. Phys. A 811, 233 (2008) ; 14. E. Pollacco et al., Eur. Phys. J. A 25, s01, 287–288 (2005).


36


37

INVESTIGATION ON PSEUDOSCALAR MESON PHOTOPRODUCTION

BY ELECTROMAGNETIC PROBE

M. Romaniuka,b,c,*

, V. De Leoa,b

, F. Curciarelloa,b

, G. Mandaglioa,b

, G. Giardinaa,b

a) Dipartimento di Fisica, Università di Messina, I-98166, Messina, Italy

b) INFN- Sezione Catania, I-95123, Catania, Italy

c) Institute for nuclear Research, National Accademy of Science of Ukraine, Kiev, 03680, Ukraine

* e-mail: [email protected]

Abstract

The Dalitz decay, second most common decay mode of 0 e e , with probability 0.01198, was

studied. Dalitz and double Dalitz decays are of interest

because they can be exploited to perform a

measurement of the electromagnetic form factor of the

decaying meson. Such mode of pions decay is a

prominent quantity in many sub-fields of particle

physics, such as chiral perturbation theory and for g-2

physics. Performed analysis of the GRAAL data and

prospective for BGO-OD for interested channel.

Introduction

The studding of the nucleon structure is one of

primary interests in the strong interaction physics and

has been the subject of experimental and theoretical

studies for several decades. To describe strong

interactions we are using Quantum Chromo Dynamics

(QCD) – the formal theory of the colour interactions

between quarks. In the high energy regime (αs<<1)

common tool to perform investigation at QCD is

perturbative approach. In low energy regime( where

αs≈1), which is typical of the nucleon and its

resonances, it is not possible to use perturbative

approach. Using different effective degrees of freedom

of the nucleon one could obtain different nucleon

resonance spectra. But up to now exist an open

problem with missing resonances: not all predicted

states was observed. The dominant decay channel for

nucleon resonances is the strong decay with single or

multi meson emission.

The excited states have strong overlapping between

the excitation curves of resonances whose masses can

differ of tens of MeV. Tools for the study of nucleon

resonances is πN experiments by electro-magnetic

probe. The availability of high intensity and high duty

cycle electron and photon facilities open new

possibilities for the study of baryon resonances using

electromagnetic probes. These provide information on

the resonances and nucleon wavefunctions through the

measurement of the helicity amplitudes, i.e. the

electromagnetic couplings between nucleon ground

state and initial states. In addition electroproduction

also allows us to explore baryon structure for different

distance scales by varying the photon virtuality.

Nowadays electro-excitation processes are a

fundamental tool to pursue these studies.

Meson Photoproduction

Experimentally, the density of states of the baryon

resonances in the mass region above 1.8 GeV is much

Figure 1: Total photoabsorption cross section

and exclusive cross sections for single-meson

and multimeson production. (a) Total, pπ0, p

p '; (b) total, K+, K

+, K

0; (c) p ,p , p ,

, , ; (d) pπ+π

-, pπ

0π

0, pπ

0

pπ+π

-π

0, pK

+K

-.

smaller than expected. A reason might be [1, 2] that

these missing resonances decouple from the πN

channel.

Then they escape detection in πN elastic scattering.

These resonances are expected to have no

anomalously low helicity amplitudes; then they must

show up in photo-production of multiparticle final

states.

From the electroproduction of baryon resonances

helicity amplitudes, form factors, and generalized

polarizabilities (inaccessible to πN scattering) can be



38

extracted. Intense experimental and theoretical efforts

have been devoted to determinations of the E2/M1

(electric quadrupole versus magnetic dipole) and

C2/M1 (longitudinal electric quadrupole versus

magnetic dipole) ratio for the N (1232) transition

amplitude. The total photoabsorption cross section

shown in Fig. 1 exhibits a large peak ( b) due to

(1232) production, shows some structures in the

second and third resonance regions, and levels off at

about b at a few GeV [3].

Polarization observables

The differential cross section for electroproduction

of pseudoscalar mesons off nucleons is given by the

product of the flux of the virtual photon field—with

longitudinal (L) and transverse (T) polarization—and

the virtual differential cross section, which depends on

six response functions (Ri = RT , RL , RTL , RTT , RTL' ,

RTT' ). The response functions depend on two additional

indices characterizing the target polarization and the

recoil polarization of the final-state baryon.

Thanks to polarization observables it is possible to

separate overlapping resonances.

The Gerasimov-Drell-Hearn sum rule

The photoproduction cross section depends on the

helicity of proton and photon. The Gerasimov-Drell-

Hearn (GDH) relates the integral over the helicity

asymmetry of the total absorption cross section for

circularly polarised photons on a longitudinally

polarised nucleon target to the nucleon anomalous

magnetic moment k, the spin S and the mass M:

2

2 2

24

th

p a

GDH

eI d k S

M (1)

where ζp and ζa are the total absorption cross

sections for parallel and antiparallel relative spin

configurations respectively, and the cross section is

weighted by the inverse of the photon energy .

The lower limit of the integral, th , corresponds to the

inelastic threshold of the reaction which, in the case of

the nucleons, is the pion photoproduction threshold.

Measurements of the helicity difference on exclusive

final states provide an important input to partial-wave

analyses.

Daliz decay

Dalitz decay, e e is the second most

important decay channel of the neutral pion with a

branching ratio of (1.198±0.032)%, while the dominant

decay mode, has a branching ratio of (98.798

± 0.032)% . The interest of the Dalitz decay lies in the

fact that it provides information on the semi off-shell

transition form factor 0 *F in the time-like

region, and more specifically on its slope parameter a .

The muon g−2 is one of the most precisely measured

and theoretically best investigated quantities in particle

physics. Our interest in very high precision

measurements is motivated by eagerness to exploit the

limits of our present understanding of nature and to

find effects which cannot be explained by the

established theory. More than 30 years after its

invention this is still the SM of elementary particle

interactions, a SU(3)c⊗SU(2)L⊗ U(1)Y gauge theory

broken to SU(3)c⊗U(1)em by the Higgs mechanism,

which requires a not yet discovered Higgs particle to

exist.

As important as charge, spin, mass and lifetime, are

the magnetic and electric dipole moments which are

typical for spinning particles like the leptons. Both

electrical and magnetic properties have their origin in

the electrical charges and their currents. Magnetic

monopoles are not necessary to obtain magnetic

moments. On the classical level, an orbiting particle

with electric charge e and mass m exhibits a magnetic

dipole moment given by

2L

eL

m (2)

where L mr v is the orbital angular

momentum. An electrical dipole moment can exist due

to relative displacements of the centers of positive and

negative electrical charge distributions. For a particle

with spin the magnetic moment is intrinsic and

obtained by replacing the the angular momentum

operator L by the spin operator

2S (3)

where is the Pauli spin matrices. Thus,

generalizing the classical form (2) of the orbital

magnetic moment, one writes

02

m gQ (4)

where 0

2

e

m, Q is the electrical charge in units

of e, Q=−1 for the leptons (l = e, μ, η ), Q=+1 for the

antileptons and m is the mass. The equations define the

gyromagnetic ratio g (g-factor) quantity exhibiting

important dynamical information about the leptons.


39

The deviation from the Dirac value g /2=1, obtained

at the classical level, is anomalous magnetic moment:

2

2

ll

ga (5)

Figure 2. Spin precession in the g−2 ring

(∼12°/circle).

The measurement of aμ is illustrated in Fig. 2 [6].

When polarized muons travel on a circular orbit in a

constant magnetic field, then aμ is responsible for the

Larmor precession of the direction of the spin of the

muon, characterized by the angular frequency

a

eBa

m (6)

From comparison standard model theory and

experiment one could obtain:

exp 1027.6 8.1 10 3.4tha a (7)

Is there ―new physics‖?

The various components of the g-2 is QED, weak

contribution, hadronic vacuum polarization and

hadronic light by light. The most problematic set of

hadronic corrections is that related to hadronic light-

by-light scattering. Such contributions can be

dramatically enhanced and thus represent an important

contribution which has to be evaluated carefully. The

problem is that even for real-photon light-by-light

scattering, perturbation theory is far from being able to

describe reality, showing sharp spikes of π0, η and η'

production, while pQCD predicts a smooth continuum.

Experimental set-up

The new experimental setup of the recently established

BGOOD collaboration consists of the combination of

an open-dipole forward spectrometer and the BGO ball

of the former GRAAL collaboration to cover the

central angular region. This configuration is ideally

suited to investigate the photoproduction of multi-

particle final states with mixed charges. In addition it

will allow nucleon polarization measurements in

single-meson photoproduction. Due to the excellent

forward acceptance it opens the possibility to

investigate vector-meson production in order to

understand the reaction mechanism and the role of

resonances.

The BGOOD collaboration presently includes

individuals and groups from Germany (Bonn), Italy

(Rome, Frascati, Pavia, Messina), Russia (Gatchina,

Moscow), UK (Edinburgh, Glasgow) and Ukraine

(Kharkov), and is open for further extension.

The experimental set-up consists of a large 90 ton

dipole magnet, tracing detectors, two scintillating fiber

detectors, MOMO and SciFi2 (to allow for momentum

reconstruction of charged particles bent through the

magnetic field), an aerogel Cherenkov detector

(discriminates pions against protons and particularly

improves the K±-identification substantially), a time-

of-flight (TOF) detector (provides flight-time

measurements for charged particles and neutrons), the

BGO Ball hermetically encloses the target (polar

angular range 25- 155 degrees). The BGO (Bi4Ge3O12)

Ball is made of 480 truncated pyramidal crystals,

mechanical structure consists 24 carbon fibre baskets

(each containing 20 crystals) and external steel support.

The baskets keeps crystals separated, mechanically and

optically. The photomultiplier tubes (readout of the

crystals) coupled directly to the crystals. By this way

obtains an excellent energy resolution also at low

energies.

The target cell is a 4 cm diameter aluminum cylinder,

closed by thin mylar windows at the two sides, filled

by liquid Hydrogen (H2) or Deuterium (D2). The target

placed along the photon beam direction and

surrounded by BGO Ball hermetically. The

hydrogen/deuterium gas is cooled down by the helium

using heat exchangers and liquefied inside the cell. The

working temperature of the liquid Hydrogen or

Deuterium is about 17 K and 22 K respectively.


40

Figure 3. The invariant γ γ mass spectrum

obtained with the Crystal Ball detector.

Figure 4. Energy balance (all quantity was directly

measured) and invariant mass in the final state: no cut

(red), a cut on Fermi momentum of Spectator in

Deuteron Target lower than 0.2 GeV/c and on Neural

Network variable higher than 0.8 were applied (black).

We are interesting in the channel with pseudoscalar

meson p PS p , wich decay to

PS e+e

- or PS e

+e

-e

+e

-. Where

pseudoscalar meson (π0, η and η') as much as possible

near threshold. Our goal is to identify (PS) thanks to

the missing mass of the system ( p–p') and then study

the PS decay product (Fig.3).

Recent relevant results of our analysis

By analysing the experimental data of Graal

experiment we identify the invariant mass of π0 and η

from Daliz decay e+e

-. About η': it is not possible to

measure with enough statistics because at Graal the

energy E is up to 1.5 GeV, only 50 MeV over the

threshold of η' production. By looking the invariant

mass obtained without any cuts application, the meson

reconstruction by two charged particle and one neutral

particle in the BGO is strongly dominate by π+π

-π

0 or

similar multiple pion channels (Fig.4).

Finally by applying our cuts, we was able to measure

and distinguish the π0 and η events, see the

reconstructed invariant mass in Fig.5. The statistics

available at Graal is not enough to extract the

observables presented in this measurement, but this

work result very promising at BGO-OD for the higher

intensity of the beam and the larger solid angle of

detection available in the new experiment.

Figure 5. Reconstructed invariant mass of π0 and η.

References [1] Koniuk, R., and N. Isgur, Phys. Rev. D 21 (1980) 1868; [2] Koniuk, R., and N. Isgur, Phys. Rev. Lett. 44 (1980) 845;

[3] Klempt E. and Richard J.-M.: Baryon spectroscopy, Rev. Mod.

Phys., Vol. 82 (2010 ) No. 2, 1-59; [4] Gerasimov S. B., 1966, Sov. J. Nucl. Phys. 2, 430, Yad. Fiz.

(1966) 2, 598; [5] Drell, S. D., and A. C. Hearn, Phys. Rev. Lett. ( 1966)16, 908;

[6] F. Jegerlehner, A. Nyffeler , Physics Reports 477 (2009) 1–110.


41

STUDY OF NUCLEAR EQUATIONS OF STATE: THE ASY-EOS

EXPERIMENT AT GSI

S. Santoroa,b

for ASY-EOS collaboration

a)Dottorato in Fisica dell’Università di Messina, Dip.to di Fisica, V.le F.S. D’Alcontres ,98166 S. Agata-Messina, Italy

b) INFN-Gruppo Collegato di Messina, Messina, Italy

The study of the symmetry energy at nuclear

densities up to few time over the saturation value (~

0.15 fm-3

) constitutes an important task to improve

knowledge for the physics of heavy ion collisions (with

stable and radioactive beams) and astrophysics due to

the strict link with neutron stars studies. The AsyEos

collaboration has proposed an experiment at GSI

(S394) in order to study the nuclear collisions 197

Au

+197

Au,96

Ru +96

Ru and 96

Zr +96

Zr at 400 MeV/nucleon

incident energy with the SIS accelerator. In this

experiment the Land neutron detector, the Aladin

ToFWall, the forward part of the Chimera device and

the Si-CsI Krakow array have been used with the goal

to study the neutron and protons elliptic flows in an

optimized experimental conditions and with improved

statistics respect to the previous Fopi experiments

devoted to measure the observables that we want to

study. The reaction Au+Au has been successfully

performed in May 2011. We will present, after a brief

summary of the main motivations of the experiment,

the first results relative to the response of various

devices used. In particular the preliminary results of

the charge high identification obtained by means fast-

slow technique in the Chimera CsI detectors will be

shown.

Introduction

A key question in modern nuclear physics is the

knowledge of the nuclear Equation Of State (EOS)

and, in particular, of its dependence on density and on

asymmetry, i.e., on the relative neutron-to-proton

abundance [1, 2, 3, 4]. The EOS can be divided into a

symmetric term (i.e., independent from the isospin

asymmetry N Z

IN Z

, where N and and Z are the

numbers of neutrons and protons, respectively) and an

asymmetric term (also known as the symmetry energy)

that is proportional to the square of the isospin

asymmetry I [3,4,5]. Measurements of isoscalar

collective vibrations, collective flow and kaon

production [1,6,7] in energetic nucleus-nucleus

collisions have constrained the behaviour of the

equation of state of isospin symmetric matter for

densities up to five times the saturation density ρ0. On

the other side, the EOS of asymmetric matter is still

subject to large uncertainties. Besides the astrophysical

interest, e.g. neutron star physics and supernovae

collapse [8,9], the density dependence of the symmetry

term is of fundamental importance for nuclear physics.

The thickness of the neutron skin of heavy nuclei

reflects the differential pressure exerted on the core

[10] and the strength of the three-body forces, an

important ingredient in nuclear structure calculations

[11], represents one of the major uncertainties in

modeling the equation of state at high density [1,12].

Moreover, properties of exotic nuclei, i.e., nuclei far

away from stability valley, and the dynamics of nuclear

reactions rely on the density dependence of the

symmetry energy [3,4]. In the last decade,

measurements of the Giant Monopole [13], Giant

Dipole [14] and Pygmy Dipole [15] resonances in

neutron-rich nuclei, isospin diffusion [16,17], neutron

and proton emissions [18], fragment isotopic ratios

[17,19,20] and isospin dependence of competition

between deep-inelastic and incomplete fusion reactions

[21] have provided initial constraints on the density

dependence of the symmetry energy around and below

saturation density ρ0. It results that the best description

of experimental data is obtained with a symmetry

energy )u(C)u(C)u(S sym

pot

3/2sym

kin with in the

range 0.6-1.1 [17] ( 0/u is the reduced nuclear

density). In the near future, extensions of these

measurements with both stable and rare-isotope beams

will provide further stringent constraints at sub-

saturation densities. In contrast, up to now, very few

experimental constraints exist on the symmetry energy

at supra-saturation densities ( 1u ). This is the

domain with the greatest theoretical uncertainty and the

largest interest for neutron stars. The behaviour of the

symmetry energy at supra-saturation densities can only

be explored in terrestrial laboratories by using

relativistic heavy-ion collisions of isospin asymmetric

nuclei. Reaction simulations propose several

potentially useful observable which should be sensitive

to the behavior of the symmetry energy at supra-

saturation densities, such as neutron and proton

flows(direct and elliptic) [4,22,23], neutron/proton

ratio [4,17,24, 25], / ratio and flows [4,22,26], 0/K K [27] and / [26] ratios.

To this day the problem is still open. Few works have

provided constraints on symmetry energy behaviour at

supra-saturation densities. The double ratio


42

Zr

0

Ru

0 )K/K/()K/K( was measured in 96

Ru

+96

Ru and 96

Zr +96

Zr collisions at 1528 MeV/nucleon

using the FOPI detector at GSI [28]; the experimental

results show good agreement with the prediction of a

thermal model in the case of the assumption of a soft

symmetry energy for infinite nuclear matter. More

realistic simulations in the frame of transport theory,

for finite nuclear matter, show a similar good

agreement with the data, but also exhibit a quite

insensitivity to the symmetry term. However, it has

recently been pointed out that more experimental and

theoretical work are needed to establish the

effectiveness of the0/K K ratio in probing the

symmetry energy [4]. The single ratio / was

measured in 197

Au +197

Au [29] and analyzed using the

hadronic transport model IBUU04 [30]. The results

suggest that the symmetry energy is rather soft at

supra-saturation densities; this finding, symmetry

energy reaches its maximum at a density between ρ0

and 2ρ0 and then starts decreasing at higher densities, is

not consistent with the density dependence deduced

from fragmentation experiments probing nuclear

matter near or below saturation density [17] and with

the slightly softer density dependence resulting from

the analysis of the pygmy dipole resonance in heavy

nuclei [15]. Moreover, other theoretical works [31]

suggest a reduced sensitivity of / ratio to the

symmetry energy. Recently, the same set of FOPI data

has been analyzed in the framework of the IMproved

Isospin dependent Quantum Molecular Dynamics (Im-

IQMD) [32]; it results a very stiff symmetry energy of

the potential term proportional to u with 2 , just

the opposite of [30] results.

Fig. 1. - Asy-Stiff (F15) and Asy-Soft (F05)

parameterizations of symmetry potential energy

of nucleons as a function of the reduced nuclear

density u, as used in UrQMD calculations; from

ref. [36]

It follows that also for the / ratio further work

is needed to establish the effectiveness in probing the

symmetry energy. In-medium absorption and re-

emission of pions can distort the asymptotic

experimental signal and it is not clear which density of

matter is explored by the pions signal. The analysis of

another set of FOPI data is described in the third

section of this paper.

Neutron and proton elliptic flows

One of the most promising probe of the symmetry

energy strength at supra-saturation densities is the

difference of the neutron and proton (or hydrogen)

elliptic flows [33,34,35]. This has emerged mainly

from calculations based on the Ultra-Relativistic

Quantum Molecular Dynamics model (UrQMD) [37].

We report here some results obtained using UrQMD

for the 197

Au+197

Au collision at 400 MeV/nucleon. The

calculations have been performed using both Asy-Stiff

( 1.5 ) and Asy-Soft ( 0.5 ) potential

symmetry energies, indicated as F15 and F05,

respectively, in Fig. 1. A realistic description of the

clustering processes during the evolution of the

reaction is crucial for predicting dynamical properties

of free neutrons, protons and light charged particles. In

the UrQMD, the clustering algorithm is based on the

evaluation of the proximity of nucleons in the phase

space by using two parameters: the relative nucleon

coordinates (Δr) and the relative momenta (Δp). The

results presented here have been obtained using the

cluster distributions built after a reaction time of 150

fm/c. The proximity parameters were: Δr=3.0 fm and

Δp=275 MeV/c which are typical for QMD models

[38]. As an example of the clusterization procedure, the

charge distribution obtained for central collisions of

Au+Au is shown in Fig. 2 in comparison with the data

of Reisdorf et al. [39]. With a normalization at Z = 1,

the overall dependence on Z is rather well reproduced

but the yields of Z = 2 particles are under predicted by

about a factor 3. The strong binding of 4He particles is

beyond the phase-space clustering criterion used in the

model. However, also the 4π integrated yields of

deuterons and tritons in central collisions are

underestimated by similar factors of 2 to 3.

The UrQMD predictions for the elliptic flow of

neutrons, protons, and hydrogen as a function of

rapidity in laboratory reference system Ylab for mid-

peripheral collisions (impact parameter 5.5 < b < 7.5

fm) and for the two choices of the density dependence

of the symmetry energy, are shown in Fig. 3. We

remind here that direct 1v and elliptic 2v flows

are obtained by the azimuthal particle distributions

with the usual Fourier expansion:

)2cos(2)cos(21)(f 11 (1)


43

Fig. 2. - Fragment yields, integrated over the

4π solid angle, in central (equivalent to impact

parameter b < 2:0 fm) collisions of 197

Au+197

Au

at 400 MeV/nucleon as a function of Z (dots,

from Ref. [29]) in comparison with UrQMD

predictions normalized at Z=1 (histogram);

adapted from Ref. [40].

with representing the azimuthal angle of the

emitted particle with respect to the reaction plane [41].

The dominant difference is the significantly larger

neutron squeeze-out in the Asy-Stiff case (upper panel)

compared to the Asy-Soft case (lower panel). The

proton and hydrogen flows respond only weakly, and

in opposite direction, to the variation of within the

interval of interest. Another interesting observable is

the ratio of neutron and proton yields as a function of

the transverse momentum pt (i.e. the component of

momentum perpendicular to the beam direction).

ASY-EOS experiment at GSI

The experiment S394, "Constraining the Symmetry

Energy at Supra- Saturation Densities With

Measurements of Neutron and Proton Elliptic Flows",

was devoted to measurements of neutron and proton

elliptic flows in isospin asymmetric systems 197

Au

+197

Au,96

Ru +96

Ru and 96

Zr +96

Zr at 400 MeV/nucleon.

Simultaneous measurements of neutron-proton yield

ratio, flow and isotopic ratio for light fragments was

performed; all these measurements could allow to

compare the symmetry energy as extracted by using

several different nucleon-based observable. The

Au+Au system is heavy and neutron-rich. Simulations

with UrQMD predict large sensitivity of the symmetry

energy on the neutron-proton observable for this

system. Using Ru+Ru and Zr+Zr systems could allow

us to compare neutron-rich and neutron-deficient

systems; the 96

Ru and 96

Zr combination is unique

among available stable isotopes in that it is mass

symmetric and isobaric. The measurement with these

systems are very important in order to reduce

systematic errors. Besides, the collected data could

provide important information to pin up effects related

Fig. 3. - Elliptic flow parameter for mid-

peripheral (impact parameter 5.5 < b < 7.5fm) 197

Au +197

Au collisions at 400 MeV/nucleon as

calculated with the UrQMD model for neutrons

(dots), protons (circles), and all hydrogen

isotopes (Z=1, open triangles), integrated over

transverse momentum pt, as a function of the

laboratory rapidity Ylab. The predictions

obtained with a stiff and a soft density

dependence of the symmetry term are given in

the upper and lower panels, respectively. The

experimental result from Ref. [42] for Z = 1

particles at mid-rapidity is represented by the

filled triangle (the horizontal bar represents the

experimental rapidity interval); adapted from

Ref. [40].

to the size, the total charge and the surface of the

nuclear system. This experiment aims to achieve high

quality of the analysis by increasing the statistics by

factor expected to be around 20-30 compared to the

previous experiments.

Fig. 4. - Schematic view of experimental setup.


44

Fig. 5. - Fast vs Slow component scatter plot as

obtained in a CHIMERA CsI(Tl) scintillator

placed at a polar angle 9lab for Au+Au

reaction at 400 MeV/nucleon at GSI; lines of

particles stopped and passing through CsI

detector are indicated by arrows.

During the experiment (see Fig. 4 for a schematic

view) we used LAND [46], time-of-flight detector for

high energetic neutrons and light charged particles in a

similar geometry like in [43] to measure neutron

squeeze-out. LAND has been positioned around

45lab , to cover the mid-rapidity for a large

transverse momentum region. Protons can be separated

by employing the calorimetric properties of the neutron

detector and the measured proton observable can be

compared directly to the FOPI data measured in a

similar angular acceptance. The simultaneous

measurement of the atomic number Z and the

azimuthal angle for fragment emissions in the forward

direction will be essential for a precise determination

of the modulus and orientation (reaction plane) of the

impact parameter; this task has been accomplished by

using a detection system with high granularity at

forward angles ( 7 20lab ) consisting of 8 CsI

rings (352 modules) of the CHIMERA multi-detector

[47] and the ALADIN Time-Of-Flight wall [48].

Preliminary results revealed a good charge

identification performance for light charged particles

using the fast-slow technique in the CsI detectors

(Fig.5) and the capability of reconstructing the reaction

plane. In addition, flow of light fragments have been

measured with the Krakow telescope array positioned

on the opposite side of LAND, at angles

( 21 60lab ). The use of digital acquisition

techniques [49] in about 10 % of the detectors, in

parallel to standard analogical one, has been of

fundamental importance allowing us to store directly

the shape the electronic signals; an off-line analysis is

then useful in order to study the best processing system

and to develop new electronic solutions.

Conclusions

New experiments on symmetry energy at supra-

saturation densities are expected to take place during

the next few years, in Europe as well as worldwide. It

is likely that providing definitive constraints on the

symmetry energy will require simultaneous

measurements of several observable. However, the

isospin signals at supra-saturation densities appear to

be controversial and strongly model dependent; to

clarify these points, we need a better understanding of

volume, Coulomb and surface effects, production and

reabsorption of resonances, reaction dynamics, in-

medium nucleon-nucleon cross section, splitting of

neutron and proton effective masses in momentum

dependent iso-vectorial interactions. Neutron and

proton elliptic flows appear to be as one of the most

interesting observable with strong sensitivity to

symmetry energy. The ASY-EOS experiment at GSI

was performed properly to measure such and other

isospin sensitive observable in reactions of isospin

asymmetric systems at pre-relativistic energies, in

order to provide quantitative information on the density

dependence of symmetry energy at supra-normal

saturation density.

The author would like to thank the people that made

this work possible: the whole INFN-CHIMERA-

EXOCHIM collaboration in Catania, Messina, Naples

and Milano, the GSI-Group and the ASY-EOS

collaboration for their support and exceptional work.

References [1] Fuchs C. and Wolter H.H., Eur. Phys. J. A, 30 (2006) 5;

[2] KlÄahn T. et al., Phys. Rev. C, 74 (2006) 035802;

[3] Baran V. et al., Phys. Rep., 410 (2005) 335; [4] Li B.-A. et al., Phys. Rep., 464 (2008) 113;

[5] Lattimer J.M. and Prakash M., Science, 304 (2004) 536;

[6] Danielewicz P. et al., Science, 298 (2002) 1592; [7] Youngblood D.H. et al , Phys. Rev. Lett., 82 (1999) 691;

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[12] Chang Xu and Li B.-A., Phys. Rev. C, 81 (2010) 064612;

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[18] Famiano M. et al., Phys. Rev. Lett., 97 (2009) 052701;

[19] Iglio J. et al., Phys. Rev. C, 74 (2006) 024605;


45

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46


47

PREMIO APP PER UNA TESI DI DOTTORATO

Paolo V. Giaquinta

Università degli Studi di Messina

Quest‘anno è stata celebrata la prima edizione del

premio conferito congiuntamente dall‘Accademia

Peloritana dei Pericolanti (APP) - segnatamente, dalla

―Classe di Scienze Fisiche, Matematiche e Naturali‖

della stessa Accademia - e dal Corso di Dottorato di

Ricerca in Fisica all‘autore della tesi di dottorato,

afferente al XXIII ciclo, distintasi particolarmente per

originalità e contenuti. La valutazione delle tesi

presentate dai candidati al premio è stata effettuata da

una commissione insediata ad hoc dal Collegio dei

Docenti del Corso di Dottorato; la commissione era

presieduta dal Prof. Lorenzo Torrisi, Coordinatore del

Corso di Dottorato, ed era composta dai Proff.

Giuseppe Carini, Giorgio Giardina, Domenico

Majolino e Paolo V. Giaquinta, quest‘ultimo anche

nella qualità di Direttore della Classe di Scienze

FF.MM.NN. dell‘Accademia Peloritana dei Pericolanti.

La commissione, riunitasi il 20 aprile 2011, ha

deliberato all‘unanimità di assegnare il premio al Dott.

Alessandro Ridolfo per la tesi intitolata “Quantum

optical properties of strongly coupled systems” , con la

seguente motivazione:

“La tesi del Dr. Ridolfo, di cui si riporta in calce il

sommario, riguarda una trattazione quantistica nel

campo dell’opto-elettronica. Nanoparticelle e

nanostrutture sono capaci di focalizzare fotoni a

dimensioni più piccole della lunghezza d’onda. In tal

modo è possibile aumentare la densità ottica degli stati

anche in una microcavità. La tesi affronta lo studio

teorico di questi sistemi quantici. Le indagini effettuate

fanno prevedere la possibilità di migliorare in futuro

dispositivi quanto-fotonici, basati su semiconduttori, di

dimensione nanometrica che possono essere sensibili

anche a fotoni singoli e che possono adoperarsi per

emissioni di luce laser da dispositivi nanometrici. La

trattazione approfondita del problema, l’approccio

quantistico adoperato, l’originalità della tematica

affrontata e le possibili ricadute applicative che i

dispositivi a semiconduttore potrebbero avere, hanno

contribuito a fare giudicare la tesi del Dr. Ridolfo di

elevata qualità, originalità e approfondimento, ben

meritevole dunque del premio in oggetto.”

L‘attestato di merito è stato consegnato dal Prof. Paolo

V. Giaquinta al Dott. Alessandro Ridolfo in occasione

della II Giornata di Studio del Dottorato di Ricerca in

Fisica. Il premio conferito dà anche titolo alla

pubblicazione di un ampio estratto della tesi sugli “Atti

della Accademia Peloritana dei Pericolanti (AAPP) - Classe di Scienze Fisiche, Matematiche e Naturali” ,

una rivista scientifica multidisciplinare pubblicata in

formato elettronico e liberamente accessibile sul

dominio internet: http://www.actapeloritana.it.

Sommario della Tesi

QUANTUM OPTICAL PROPERTIES OF STRONGLY

COUPLED SYSTEMS

“The realization of solid state devices able to control

the single photon states is of great importance in the

field of Quantum Information and Opto-electronics. Re- cently, significant developments have been

achieved by coupling single quantum emitters (QEs) in

optical microcavities with high Q factor. The main

limitation of these devices is represented by the size of the cavities that can not be smaller than half wavelength, and in practice are much larger because of the presence of mirrors or photonic crystals required to

obtain the optical confinement. However, nanoparticles (NPs) and metallic nanostructures are able to

focus the electromagnetic waves to spots much smaller

than a wavelength. In this way, it is possible to increase

the optical density of states, as well as with the

microcavity, but with more compact structure. The

ability of metal NPs to control the radiative decay of the QEs nearly positioned has been widely

demonstrated both theoretically and experimentally. In

this thesis I’ve been studied, from the theoretical point

of view, the optical properties of these quantum

systems, in various coupling regime. In the first part it

was developed a theoretical framework based on the

calculation of the Master Equation (ME), which has

helped to investigate the photoluminescence’s

properties of microcavity coupled to QEs optically

excited via incoherent pumping. In such systems, under

low excitation density, it was possible to obtain

analytical formulas that describe the processes

associated with the first-order correlations

(photoluminescence spectra). The results obtained from

the fit of the experimental data show an excellent

agreement with our theoretical results. In particular, it has been shown highly predictive nature in the case of photonic polaritons in an organic double microcavity: the fit of the photoluminescence of one of the two

microcavities has enabled the calculation of the

photoluminescence of the whole structure (A. Ridolfo

et al. Phys. Rev. B 81, 075313 (2010)). At high-density

excitation, calculation’s technique in non-perturbative

regime (based on the truncation of the number of photons) has led to some important results in the study

of nonlinear optical processes. Subse- quently, the ME

formalism was extended to the case of structures made

http://www.actapeloritana.it/


48

of metal NPs coupled to QES that, because of their

spectroscopic properties, are also called artificial

hybrid molecules. The extension of the theoretical

framework was made possible by modeling the

appropriate electromagnetic field which arises from the

presence of electronic excitations on the surface of metal NPs called plasmons. The results, which refer to

the silver NPs, show that the inelastic part of the

resonance fluorescence increases more than two orders

of magnitude than the QE alone. It also reported a

careful study of the statistical properties of the

scattered light by calculating the second order

correlation function, which is strongly influenced by

the presence Fano effect, originating from the

interaction between the QE discrete excitation and the

continuous band of plasmon. The calculation of the

scattering spectra and of the intensity correlations, shows that this system can be used as a single photon

ultra-compact optical transistor: the scattering of a first

photon of appropriate frequency, is able to activate (or

inhibit) the scattering of a second photon (A. Ridolfo et

al., Phys. Rev. Lett (in press)). In the next chapter, with

accurate calculations of electromagnetic scattering

based on the T-matrix, it has been demonstrated that it

is possible to realize the strong coupling regime in the

case of many QEs and single QE (S. Savasta et al., ACS Nano, 4, 6369 - 6376 (2010)). In the first case, the cross section of extinction, calculated for a

structure consisting of a silver nanoparticle coated with

a dielectric matrix doped with photoluminescent

molecules, has showed the characteristic anticrossing

typical of the strong coupling regime. In the second

case, replacing the single-nanoparticle geometry with

the two-nanoparticle geometry in order to obtain an

increase of the plasmonic field in the center of the

principal axis to obtain the strong coupling regime with

a single QE. Again, calculations have showed the

achievement of the regime of strong interaction in a

structure whose maximum size is only 40 nm! From

the results obtained thus good prospectives emerge for

possible applications in Quantum Information or to

create devices that can process individual photons. This

will make it possible to implement devices for

Photonic Quantum Computation without renounce to

the nanometric dimensions of the compact modern

nano-sized semiconductor logical gates. In the second-last chapter has been presented a theoretical analysis of all-optical control of the strong coupling regime

(dynamic switching-on/off) between a single QE and

an optically confined microcavity-mode, by sending

optical pulses control of appropriate area, able to

determine transitions to and from the third lower level

energy of the QE (A. Ridolfo et al., Phys. Rev. Lett (in

press)). The chosen scheme describes the system

recently used in experiments on adiabatic- switching

for inter-sub-polaritons (Guenter G. et al. Nature 458, 178 (2009)), but it can also be applied to the study of optical transitions exciton-biexciton cascade or other

transitions, in which are present the cavity polaritons. From our results, important conclusions are drawn

about the possibilities and limitations of the important

experimental design proposed: once Rabi oscillations

have been induced with a first control pulse, depending

on the time of arrival of a second control pulse, Rabi

oscillations can be suppressed or not, also influencing

the coherence properties of the whole system. The

theoretical results obtained are very fascinating and

will stimulate the achievement of new experimental

and technology goals.

Finally, in the last chapter it has been studied the

dynamic behavior of entanglement in a system

consisting of two solid state QEs enclosed in two

separate microcavities. In this solid state system, in

addition to coupling with the cavity mode, the QE is

coupled to a continuum of modes that provide a lossy

channel to which is adds a further loss caused by the

phases losses induced by interaction with thermal

phonons. This configuration has been modeled as a

multiparty system consisting of two independent sub-parts, each containing a single q-bit and a single cavity

mode, subject to losses, radiative and non-radiative

decay (pure-dephasing). The theoretical results

obtained by the usual framework of ME already used

in previous chapters have highlighted the important

destructive impact on the evolution of entanglement-dynamics caused by pure-dephasing. The experimental

information in these systems can be obtained from the

detection of the light escaping from the cavity. With an

appropriate choice of physical parameters of the model, corresponding to values that are extrapolated from the

experiments, was simulated the dynamic evolution of entanglement in two realistic situations (K. Hennessy

et al. Nature 445, 896 (2008) V . Loo V et al. arXiv: 1011.1155v1 [cond –mat.mes-hall] (2010)). Thus, the

work places emphasis on the negative impact of pure-dephasing, always present in solid state devices, on the

entanglement decay.”


49

PHD E MONDO DEL LAVORO: STATISTICHE SUL PLACEMENT POST –

DOTTORATO

Paola Donato

Dipartimento di Fisica, Università di Messina

Dottorato di Ricerca in Fisica, Università di Messina

1. Introduzione

È stato sfruttato il database del dottorato di ricerca in

Fisica per condurre un‘indagine sul placement dei

dottori di ricerca in Fisica dell‘Università degli Studi di

Messina relativamente ai cicli dal XIII al XXIII.

Occorre premettere che si è fatto in modo di curare e

far crescere il database del dottorato, strumento

indispensabile per questo tipo di analisi. Il database,

infatti, è stato avviato sin dal primo ciclo di dottorato

(1983) e, di anno in anno, aggiornato e integrato.

Ritengo sia di importanza fondamentale curare e

migliorare i dati in nostro possesso, poiché questi sono

in grado di restituirci una visione globale del lavoro

svolto dai docenti e dai dottorandi, oltre che una

valutazione complessiva della funzione didattico-

formativa del dottorato in vista della collocazione nel

mondo della ricerca e del lavoro. Proprio di

quest‘ultimo aspetto mi sono occupata in questa breve

indagine.

Altra importante premessa, inoltre, riguarda la scelta

di collocare questa indagine all‘interno di un range

temporale ristretto agli effettivi impieghi dichiarati da

sessanta dottori di ricerca in Fisica, dottorati negli

ultimi dieci anni (dal XIII al XXIII ciclo) presso il

Nostro Ateneo.

2. Macro-aree di impiego lavorativo post-doc

Per descrivere l‘andamento dell‘occupazione post-

dottorato si è ritenuto opportuno suddividere la

collocazione dei dottori di ricerca in Fisica in quattro

macroaree di impiego. Se da un lato, infatti, le

macroaree risultavano facilmente individuabili – i dati

rilevati evidenziavano la presenza di queste quattro

principali aree di impiego –, dall‘altra parte si voleva

tener conto di quegli sbocchi lavorativi meno presenti

per locazione geografica e/o territoriale, in modo tale

da rendere il futuro confronto con i dati statistici di altri

atenei il più possibile coerente.

Le aree scelte sono state quattro:

Università: All‘interno di questa macroarea

sono stati considerati i dottori di ricerca che a

oggi ricoprono il ruolo di ricercatori di ruolo,

ricercatori a tempo determinato, gli assegnisti

di ricerca, i borsisti post-doc;

Scuola: All‘interno di questa macroarea

rientrano tutti quei dottori di ricerca che sono

attualmente impiegati nella scuola secondaria

superiore;

Enti di ricerca e industrie: All‘interno di

questa macroarea abbiamo considerato quei

dottori di ricerca che sono occupati presso:

INFN, CNR, ENEA, Fondazioni, ST-

Microelectronics;

Altro: All‘interno di questa macroarea

abbiamo inserito tutte quelle attività lavorative

che non rientrano nelle tre precedenti aree.

3. Densità dei cicli

Un aspetto importante che si è deciso di prendere in

considerazione prima di addentrarci nel dettaglio delle

collocazioni lavorative dei dottori di ricerca, è stato

quello della scelta del curriculum all‘interno del corso

di dottorato. Il grafico (A) evidenzia che la principale

scelta dei dottorandi riguarda il curriculum di Struttura

della Materia, affiancato da quello di Fisica Nucleare e

seguito a distanza dai curricula di più recente

istituzione, cioè quelli di Fisica Applicata ai Beni

Culturali, di Fisica Applicata ai Beni Ambientali e

quello di Fisica della Materia Soffice e dei Sistemi

Complessi. L‘interesse del dato, ovviamente, risiede

nella sua successiva declinazione in funzione

dell‘impiego lavorativo. Ci è sembrato interessante, in

altre parole, rilevare come e in che misura la scelta del

curriculum può condizionare la tipologia di impiego

lavorativo post-doc. Occorre tenere presente che il dato

analizzato, di per sé già interessante, risulterà più

significativo quando disporremo di maggiori

informazioni relative ai curricula di più recente

istituzione.


50

DENSITA’

DEI

CICLI

CICLO Struttura della

Materia

Fisica

Nucleare

Fisica della

Materia

Soffice e dei

Sistemi

Complessi

Fisica

Applicata ai

Beni

Culturali

Fisica

Applicata ai

Beni

Ambientali

XIII 4 1

XIV 5

XV 4

XVI 2 3 1

XVII 4 1

XVIII 3 2 2

XIX 4 2

XX 3 3 1

XXI 3 1

XXII 3 1 1

XXIII 4 1 1

Grafico A: Numero dei dottorandi di ricerca in Fisica divisi per curriculum dal ciclo XIII al ciclo XXIII

4. Dottorandi divisi per curriculum scelto

all’interno del Corso di Dottorato di Ricerca

e loro placement.

Il rapporto tra la densità dei cicli e l‘impiego

lavorativo post-dottorato ha consentito di individuare

quanto la scelta del curriculum abbia influenzato lo

sbocco lavorativo. Il numero dei dottori di ricerca che

hanno scelto il curriculum Struttura della Materia e

Fisica Nucleare – maggiore perché questi curricula

sono stati istituiti da maggior tempo rispetto agli altri –

è preponderante in tutti gli ambiti lavorativi. Desidero

evidenziare che sono i soli presenti nell‘ambito

universitario, probabilmente perché i relativi settori di

applicazione, a livello sia nazionale sia internazionale,

offrono maggiori opportunità di impiego.

I dati sono indicativi anche per ciò che riguarda

l‘impiego nel settore scolastico. Pur non essendo

storicamente l‘insegnamento uno degli sbocchi naturali

per i laureati in Fisica, nondimeno è possibile rilevare

come il mondo scolastico rappresenti una risorsa

lavorativa importante per coloro che conseguono un

dottorato di ricerca. Il dato riportato nel grafico (B),

più in particolare, ci restituisce una distribuzione nel

settore scolastico pressoché equa tra tutti i curricula

del dottorato.

Importante sbocco lavorativo, inoltre, è quello degli

enti di ricerca, quali, ad esempio, INFN, CNR, ST

XIII XIV XV XVI XVII XVIII XIX XX XXI XXII XXIII

0

1

2

3

4

5

Struttura della Materia

Fisica nucleare

Fisica della Materia Soffice e Sist. C.

Fisica Applicata ai Beni Culturali

Fisica Applicata ai Beni Ambientali

Densità

Ciclo


51

Microelectronics, Arpa. Non sono presenti in questa

macroarea, come evidenzia il grafico B, dottori di

ricerca in Fisica Applicata ai Beni Culturali e Beni

Ambientali. Quasi sicuramente quest‘ultimo dato è

legato ad una scelta di specializzazione che, già a

monte, è orientata ad una implementazione

maggiormente operativa delle conoscenze acquisite.

Quasi tutti i curricula, infine, contribuiscono alla

macroarea che abbiamo definito ―altro‖.

Scuola Università Enti di Ricerca Altro Totale

Struttura della Materia 9 21 4 2 36

Fisica Nucleare 2 9 4 1 16

Fisica della Materia

Soffice e dei Sistemi

Complessi

/ / 1 1 2

Fisica Applicata ai Beni

Culturali 3 / / / 3

Fisica Applicata ai Beni

Ambientali 2 / / 1 3

Totale 16 30 9 5 60

Grafico B: Dottorandi divisi per curricula scelto all’interno del Corso di Dottorato di Ricerca e loro placement.

Scuola Università Enti di Ricerca Altro

0

5

10

15

20

Struttura della Materia

Fisica nucleare

Fisica della Materia Soffice e Sist. C.

Fisica Applicata ai Beni Culturali

Fisica Applicata ai Beni Ambientali

Densità

Occupazione

5. Densità occupazionale

Considerando in modo più generalizzato il dato

relativo all‘impiego dei dottori di ricerca, prescindendo

cioè dal curriculum scelto, risulta una suddivisione

nelle macroaree come riportato nel grafico (C).


52

DENSITA’

OCCUPAZIONALE

CICLO SCUOLA UNIVERSITA’ ENTI DI

RICERCA

ALTRO TOTALE

XIII 1 4 5

XIV 1 2 1 1 5

XV 3 1 4

XVI 3 2 1 6

XVII 1 2 2 5

XVIII 4 2 1 7

XIX 1 5 6

XX 1 3 2 1 7

XXI 3 1 4

XXII 2 1 2 5

XXIII 1 4 1 6

TOTALE 16 30 9 5 60

Grafico C: Numero dei dottori di ricerca in Fisica dal ciclo XIII al ciclo XXIII e loro placement.

Il ruolo principale nel placement dei dottori di

ricerca viene svolto dall‘istituzione universitaria. Nel

grafico (D) si è cercato di evidenziare il rapporto tra i

dottori di ricerca che sono stati assorbiti dal mondo

universitario in modo strutturale e quelli che non hanno

ancora una collocazione stabile. Ci siamo soffermati su

questo aspetto sia per sottolineare come, in modo

analogo ad altri settori lavorativi della nostra società,

anche nel mondo universitario il lavoro precario svolga

una funzione preponderante rispetto a quello stabile,

sia per confrontare il dato in nostro possesso con

un‘altra importante realtà universitaria nazionale.

S c u o la U n i v e r s it à E n ti d i R i c e r c a A l tr o

0

5

1 0

1 5

2 0

2 5

3 0

De

ns

ità

O c c u p a z io n e


53

Grafico D

Come si può rilevare dal grafico (E), infatti, il dato

tendenziale risultante dai dati messi a disposizione

dall‘Università degli Studi di Roma Tor Vergata dal

XVIII al XXIII ciclo sono identici a quelli risultanti

dagli undici cicli presi in considerazione nell‘ateneo

messinese. Questo conferma che solo circa un quarto

dei dottori di ricerca riesce a rimanere in modo

permanente all‘interno del mondo universitario. Un

altro dato rilevante, a nostro parere, è che circa un terzo

degli strutturati viene assorbito dalle Università

straniere. Questo dato è importante perché conferma la

spendibilità all‘estero delle competenze acquisite nel

nostro dottorato di ricerca, sebbene ci ricordi, nel

contempo, che molte delle nostre migliori risorse non

riescono a trovare spazio nel mondo del lavoro e della

ricerca a livello nazionale.

Grafico E

6. Placement dei dottori di ricerca: un

confronto.

Nell‘ultimo grafico sviluppato (F) abbiamo messo a

confronto le tipologie occupazionali dei dottori di

ricerca in Fisica dell‘ateneo messinese e di quello

romano (Università Tor Vergata). Questo confronto è

finalizzato innanzitutto a comprendere le diverse

opportunità che il territorio offre a coloro che

proseguono gli studi universitari conseguendo il titolo

di dottore di ricerca. Ovviamente il dato si basa su

indicazioni che non possono essere considerate

esaustive, cosa che implicherebbe una ricerca a spettro

molto più ampio rispetto a quello preso in

considerazione in questa sede. Nondimeno, con il

proposito di estendere ed approfondire in futuro i dati

che ci saranno messi a disposizione da altri atenei

italiani, riteniamo che questo grafico possa essere

rappresentativo di una situazione di fatto comunemente

nota. Il dato più evidente, in particolare, è il ruolo

svolto dalla scuola nel placement post-dottorato nei

due atenei. Se nella realtà messinese, infatti, più di un

D ot to ra to in Fisica Di M e ssin a

Are a o ccup a zio n a le : Un ivers ità

7 3,3 3%

1 6,6 7%

1 0 %

S tru ttu ra ti Estero

S tru ttu ra ti I ta lia

No n S tru t tu rat i

73 ,3 3 %

2 6,67 %

S tru ttu ra ti

No n S tru ttura ti

Area o ccu p azio na le U nive rsità

To r Ve rg a ta - R o m a


54

dottore di ricerca su quattro trova impiego in ambito

scolastico – un dato, quest‘ultimo, che proietta la

scuola al secondo posto tra le quattro macroaree prese

in considerazione –, nella realtà romana il placement

nella scuola è quasi nullo, occupando, in percentuale,

meno di tre dottori di ricerca su cento. Il dato non

evidenzia maggiori opportunità di lavoro

geograficamente localizzate nel comprensorio

messinese-siciliano rispetto a quello romano,

considerando che parte di coloro che si dedicano

all‘insegnamento cercano e trovano la collocazione

geografica della propria professione tanto a sud quanto

al centro-nord d‘Italia. Questo significa, in altre parole,

che l‘insegnamento, come sbocco di lavoro post-

dottorato, non è un dato fortemente condizionato dal

territorio, se non per un retaggio culturale che

richiederebbe, tuttavia, una analisi alquanto diversa da

quella sviluppata in questa sede.

Il secondo dato che emerge in modo evidente è che

mentre l‘Università svolge un ruolo pressappoco

uguale nella collocazione dei due atenei, diversa è la

collocazione dei dottori di ricerca presso gli enti di

ricerca. Benché, infatti, la macroarea dei dottori di

ricerca messinesi che approdano agli enti di ricerca sia

significativa – il 15% è un dato sicuramente positivo –

non si può fare a meno di notare che il dato tendenziale

relativo a questa macroarea nell‘ateneo romano sia di

rilevanza assoluta, attestandosi intorno al 40%.

Non v‘è dubbio che altre e più ampie riflessioni

potrebbero essere sviluppate a partire dagli elementi in

nostro possesso. Mi preme tuttavia sottolineare, in

conclusione, che dati e analisi riportati in questa

indagine vanno presi in considerazione in una

prospettiva tendenziale e approssimativa, nel senso che

quelli presentati in questa relazione sono soltanto i

primi elementi di una ricerca che tende, per sua natura,

ad un‘ampia raccolta di informazioni che verrà

approfondita nel corso dei prossimi mesi. Pur essendo

parziali, tuttavia, i dati a disposizione appaiono già

significativi, a condizione, evidentemente, che vengano

declinati in una chiave di lettura volta a comprendere la

continua e rapida evoluzione del mondo del lavoro e la

necessità che l‘istituzione universitaria riesca ad avere

una sempre maggiore conoscenza e coscienza del

placement di laureati e dottori di ricerca.

Grafico F: Occupazione totale dei dottori di ricerca: un confronto

Università degli Studi di Messina Università degli Studi di Roma

Tor Vergata

Bibliografia [1] Activity Report 2010, Dottorato di Ricerca in Fisica

dell‘Università di Messina, L.Torrisi Ed. ISSN n° 2038-5889,

2011-11-25

[2] Sito WEB Università degli Studi di Roma Tor Vergata:

http://dottorati.uniroma2.it/

8 ,33 %

15 %

5 0%

26 ,67 %

U nive rs ità

Scu ol a

E nti

ri cer ca

Al tr o

14,29%

40%

42,86%

2,86%

UniversitàScuola

Enti

ricerca

Al tro

http://dottorati.uniroma2.it/


55

AN OVERVIEW OF RESEARCH ACTIVITIES IN THE PHYSICS PHD

COURSE

F. Caridia,b

, L. Torrisic,d

a)Facoltà di Scienze MM. FF. NN., Università di Messina, Viale F. Stagno d’Alcontres, 31 – 98166- Messina, Italy.

b)INFN-Sez. CT, Gr. Coll. di Messina, Viale F. Stagno d’Alcontres, 31 – 98166- Messina, Italy.

c)Dipartimento di Fisica, Università di Messina, Viale F. Stagno d’Alcontres, 31 – 98166 – Messina, Italy.

d)INFN-LNS, Via S. Sofia 44, 95124, Catania, Italy.

Abstract

An overview of research activities of the PhD course

in Physics of the Messina University is reported. The

research is developed mainly in the areas of matter

structure, applied, theoretical and nuclear physics.

Many different laboratories are available for PhD

students: laboratory of plasma physics; laboratory of

acoustic and dielectric spectroscopy; laboratory of

spectroscopy, biophysics and applied physics;

laboratory for studying nuclear reactions on nucleons

and nuclei; laboratory of IR and Raman spectroscopy;

nuclear physics laboratories; laboratory of low

temperature physics; laboratory of computational

physics; laboratory of microanalysis, spectroscopic

techniques and nanomaterials; laboratory of optical

spectroscopy and laboratory of spectroscopic analyses.

A particular attention is given to collaborations of

research groups and issues covered by PhD theses in

recent years.

Introduction

The Doctorate in Physics of the Messina University

has the aim to provide a satisfactory degree of

competence and professionalism in the field of

Condensed matter, Nuclear Physics, Bio-Physics and

cultural heritage and environmental Applied Physics.

The research activities are developed mainly at the

Physics Department and at the Matter Physics and

Electronic Engineering Department of Messina

University, at the National Institute of Nuclear Physics

(INFN) and at the Institute for Chemical and Physical

processes (IPCF) of Messina CNR.

Many other national and international collaborations

also give the possibility to improve the scientific

knowledge of PhD students, working in big facilities of

last generation.

Research laboratories

The laboratories of the PhD course are reported in

Table I.

Laboratory Responsible

Laboratory of plasma physics Prof. L. Torrisi

Laboratory of acoustic and dielectric

spectroscopy

Prof. M. Cutroni

Laboratory of spectroscopic

techniques, biophysics and applied

physics

Prof. S. Magazù

Laboratory for studying nuclear

reactions on nucleons and nuclei

Prof. G. Giardina

IR and Raman Spectroscopy

Laboratory

Prof. D. Majolino

Nuclear Physics Laboratories Prof. R.C. Barnà

Laboratory of low temperature physics Prof. G. Carini

Laboratory of computational physics Prof. C. Caccamo

Laboratory of microanalysis,

spectroscopic techniques and

nanomaterials

Prof. F. Neri

Laboratory of optical spectroscopy Prof. G. Mondio

Laboratory of spectroscopic analyses Prof. L. Silipigni

Tab. I: Research laboratories of the PhD course

LABORATORY OF PLASMA PHYSICS

Instrumentation: Laser Nd:YAG, 1064 nm e 532

nm, 3 ns, 0-300 mJ, mass quadrupole spectrometer

with energy filter HIDEN EQP 300, classic mass

quadrupole spectrometer BALZERS PRISMA 300,

Langmuir probe, optical spectroscope, Faraday cup for

time-of-flight measurements, optics and vacuum

systems, detection electronics (Fig. 1).

Research activity: the experimental setup consists

in a Nd:Yag laser, operating at 1064 and 532 nm, with

a pulse width of 3 ns and maximum energy of 300 mJ.

The beam is focalized through a optical lens at a

distance of 50 cm, in order to have, in the solid target,

inside a vacuum chamber, a laser spot of around 1 mm2


56

at pressure of the order of 10-6

mbar. The interaction of

the beam with the target produces an ablation and

consequently plasma generation [1].

Applications: diagnostic of plasma laser-generated,

deposition of thin films (Pulsed Laser Deposition),

laser welding, nuclear physics (Laser Ion Source, D-D

fusion), cultural heritage applications (compounds,

isotopic ratios, surface patina analysis).

Fig. 1: Experimental setup of the Laboratory of

Plasma Physics of Messina.

Collaborations: INFN-LNS, ASCR PALS Lab.,

Institute of Plasma Physics and Laser Microfusion,

University of Pisa, Salento, Roma Tor Vergata and

Milano-Bicocca, CELIA (Centre Lasers Intenses et

Applications), MT-LAB, Bruno Kessler foundation.

LABORATORY OF ACOUSTIC AND

DIELECTRIC SPECTROSCOPY

Instrumentation: setup for ultrasound analysis

(MATEC TB1000 e MATEC 6000), setup for wide

band measurements, wave guides.

Research activity: condensed states physics. It

principally concerns problems of disorderly systems

behavior. Different techniques, structural and

dynamics, are employed: ultrasound (kHz-MHz), fully

employed in physics and engineering for non-

destroying tests (NDT), dielectric spectroscopy

(systems for wide band measurements 10-3

Hz - 2

GHz), to measure the real part ε '(ω), and the imaginary

part ε (ω), of the complex permittivity of a material

(solid, liquid) in a wide range of frequency 10-3

Hz-2

GHz, at temperatures between 450 °K and 3 °K using

only one sample. Wave guides (8.2 GHz – 40 GHz) are

also employed for measurements of the complex

permittivity at a frequency in the microwave range

with transmission lines at rectangular wave guides and

at temperatures between the room value and 10 °K [2].

Collaborations: University of Pavia, CNR–ITC,

Arizona State University, Texas Tech University,

Universidad Autonoma de Madrid, Chalmers

University of Technology.

LABORATORY OF SPECTROSCOPIC

TECHNIQUES, BIOPHYSICS AND APPLIED

PHYSICS

Instrumentation: experimental setup for static and

quasi-elastic scattering measurements, infrared

spectrometer for biophysics measurements.

Research activity: the laboratory disposes of top-

table devices (spectroscopic techniques of elastic type,

quasi-elastic and inelastic of electromagnetic radiation)

useful to the dimensional and morphologic, qualitative,

structural, dynamic and thermodynamic

characterization of a wide class of materials of

physical, biotechnological and industrial interest. The

laboratory also disposes of instrumentation for

measurements and analysis for ambient studies

(electromagnetic pollution, air pollution, …) [3].

Applications: investigations about the mechanisms

of bio-protection, micro-emulsion, gel micro-emulsion,

innovative materials, physical and chemical properties

of macro-molecular and polymeric systems of

biological interest and optimization of physical devices

for energetic and industrial fields.

Collaborations: LDSMM (CNRS), CEMHTI

(CNRS), Institute Laue Langevin, Rutherford Appleton

Laboratory, BENSC, ESRF, Soleil, Sanofi-Aventis,

Dompè, Labplants, Cosmetic Valley, ESA, Cape Town

University.

LABORATORY FOR STUDYING NUCLEAR

REACTIONS ON NUCLEONS AND NUCLEI

Research activity: study of barionic resonances by

mesons photoproduction at the facility ELSA in Bonn

(Germany) within the international cooperation

BGOOD. The Messina group in BGOOD has the tasks

of experimental setup simulations (activity carried out

in site) and of hardware and software administration of

hydrogen and deuterium cryogenic liquid target

(activity carried out in site and at ELSA).

Study of reactions induced by heavy ions for the

production of superheavy elements. The experimental

activity is carried out at China Institute of Atomic

Energy (CIAE) in Beijing (China). Activity of

calculation, experimental data analysis and

interpretation is carried out in site.

Study of Bremssthralung radiation emitted during

spontaneous fission processes and alpha decay of

heavy elements [4].

Collaborations: Institute for Nuclear Studies,

Division of Nuclear and Particle Physics, Helmholtz-

Institut fuer Strahlen und Kernphysik, Institut fuer

Kernphysik, Institut fur Experimentelle Kernphysik,

Institute for Theoretical and Experimental Physics,

Institute of Physics Jagiellonian University, Ivane

Javakhishvili State University of Tbilisi, Joint Institute

for Nuclear Research,

National Central University Jhongli, University of

Bonn, Physikalisches Institut University of Bonn,

MQS IC

Laser

Vacuum chamber


57

Helmholtz Institut f¨ur Strahlen- und Kernphysik,

Petersburg Nuclear Physics Instute, University Roma

Tor Vergata and INFN Roma2, INFN Roma1, INFN

Laboratori Nazionali di Frascati, University of Pavia

and INFN Pavia, University of Edinburgh, University

of Kharkov, University of Moscow, Bogoliubov

Laboratory for Theoretical Physics of JINR, Flerov

Laboratory for Nuclear Reaction of JINR, Institute for

Nuclear Research of NASU, Lomonosov Moscow

State University.

IR AND RAMAN SPECTROSCOPY

LABORATORY

Instrumentation: Interferometry Spectrometer

BOMEM DA8 for IR absorption measurements in

Fourier Transform (FT-IR), for measurements in

Attenuate Total Reflectivity (ATR), for FT-IR micro-

spectroscopy and Raman scattering measurements in

Fourier Transform.

Pulverizer, hydraulic press, digital balance and

electric stirrer with temperature control (50 °C – 350

°C) to prepare and store samples.

Portable XRF Analyzer ―Alpha 4000‖ Innov-

Xsystems for X-Ray Fluorescence measurements

(XRF).

Research activity: complete characterization of

dynamic and structural and/or compositional properties

of matter, both in liquid state and solid state by the use

of complementary spectroscopic tecniques. Thanks to

the not invasivity of the techniques, these

spectroscopic methodology can surely find a large and

natural application in a lot of fields nowadays

fundamental [5].

Applications: archeometry, characterization, storage

and recover of cultural heritage, biomedicine and/or

biophysics.

Collaborations: BENSC (BErlin Neutron Scattering

Center), ESRF (European Synchrotron Radiation

Facility), ILL (Institut Laue-Langevin Facility), ISIS

Rutherford-Appleton Laboratory Oxford, LLB

(Laboratoire Lèon Brillouin).

Nuclear physics laboratories

RADIATION PROCESSING LABORATORY

Instrumentation: Linac of electrons of 5 MeV

(nominal energy 5 MeV, peak current 1-200 mA, pulse

time 3 sec, peak power 1 MW, power 1 kW,

repetition frequency 1-300Hz, frequency RF 2.997

GHz, No. accelerating cavities 9, no magnetic lens,

beam diameter 4 mm).

Applications: creation of new hydrogels,

improvement of mechanic properties of UHMWPE and

wood properties by impregnation and irradiation, study

of the gas diffusion in irradiated Black PE, filament

winding, dejection of mycotoxins of food flour,

substances released during the irradiation of different

types of PE, radiative treatment of adhesive joints for

structural-type applications in the aerospace and

automobile field, recognizing of materials by non

destructive testing techniques, calibrations to recognize

irradiated foods, development of new dosimeters for

radiation processing and project of accelerating

systems for industries interested [6].

INFORMATICS LABORATORY

Instrumentation: cluster of parallel computation (6

double-processors + file server). Protocols of Parallel

Computation: PVM (Parallel Virtual Machine), MPI

(Message Passing Interface).

Research activity: Monte Carlo Simulation of

radiation processing treatments by MCNP-4C2 code

(Monte Carlo N Particle, version 4C2) and data

analysis relative to experiments carried out with the

CHIMERA multidetector (LNS).

APPLIED NUCLEAR PHYSICS LABORATORY

Instrumentation: lecture systems for optical

dosimeters (Gafchromic) and rivelation system of

cooling Ge(Li) + spectrometer α.

Research activity: dose and dose-rate

measurements, environmental radioactivity

measurements (Radon measurements on samples of

aspirated air on porous filters, radioactivity

measurements in drinking water and on building

materials).

Collaborations: INFN, Institute for Physics and

Nuclear Engineering, Institute of Physics, University of

Silesia, Institute of Physics, Jagellonian University,

Institute de Physique Nucleaire, IN2P3-CNRS and

Université Paris-Sud Orsay, LPC, ENSI Caen and

Université de Caen, Saha Institute of Nuclear Physics,

Kolkata, GANIL, CEA, IN2P3-CNRS Caen, Institute

of Nuclear Physics Cracow, Institute of Modern

Physics Lanzhou, Institute of Experimental Physics

Warsaw University.

LABORATORY OF LOW TEMPERATURE

PHYSICS

Experimental techniques: mechanical spectroscopy

and ultrasounds; low and high temperature calorimetry;

Brillouin and Raman spectroscopy; low temperature

techniques; high magnetic fields; preparation of glasses

and polymers.

Topics: influence of the disordered topology on the

physical properties of materials; glass transition; low

energy excitations; vibrational and relaxation

dynamics.


58

Research activity: solid state physics. Materials:

glasses and polymers [7]. Collaborations: Institut für Festkörperforschung,

Forschungszentrum Jülich, IPCF-CNR Messina,

Institute of Macromolecular Chemistry, National

Academy of Sciences of Ukraine, IMEM-CNR Parma,

Institute Laue-Langevin Grenoble, Department of

Chemistry and Department of Physics and Astronomy,

University of Tennessee.

LABORATORY OF COMPUTATIONAL

PHYSICS

Instrumentation: Parallel Cluster made of 10 PC

Pentium R Dual Core E5300 @ 2.60GHz 10Gb RAM,

4Tb, at the Department of Physics; parallel cluster

made of 20 knots equipped with 4 Dual Core AMD

Opteron Processor 280 and 4Gb RAM for each one (ex

TriGRID project), allocated at the Center for Electronic

Computing ―A. Villari‖; access to grid managed by the

Consorzio Cometa (http://www.consorzio.cometa.it)

among the project PI2S2 (http://www.pi2s2.it).

Research activity: Statistical mechanical study of

microscopic properties, structural and thermodynamic

properties (including the phase equilibria) of simple

and complex fluids. Integral theory of a fluid state for

single site or several sites of interaction (Ornstein-

Zernike equation, RISM Theory - Reference

Interaction Site Model). Monte Carlo simulation

methods and dynamic molecular models applied to

both monatomic and molecular fluids, either pure or

mixed.

Collaborations: Laboratoire de Physique des

Milieux Denses, Université de Metz, France, School of

Physics University of Kwazulu-Nathal,

Pietermaritzburg, South Africa, CNR-IPCF Messina,

University ―La Sapienza‖ Rome.

Laboratory of microanalysis, spectroscopic

techniques and nanomaterials

LABORATORY OF MICROANALYSIS

Instrumentation: microanalysis, imaging and depth

profiling using XPS, high yield (tens of analysis/day),

visual control of positioning for the microanalysis,

argon ion gun for removing surface layers, electron

gun to reduce the effects of electrical charging of

insulating materials, software and libraries for the

automatic recognition of the chemical composition.

Automated setup for measuring dc electrical

conductivity as a function of temperature (100-550 °K)

using the volt-amperometric method for voltage or

constant current. The system is equipped with a

cryostat cooled with liquid nitrogen with optical

windows, to measure photoconductivity.

Measurements of profilometry and roughness on

surfaces by scanning with lateral resolution of about 10

microns, and vertically up to 10 Å (Profilometer KLA-

Tencor Alpha Step 500).

Research activity: physical-chemical diagnostics,

morphological, structural and electrical engineering,

micro- and nano-scale solid surfaces and thin film

multilayer structures. By means of X-ray

photoemission spectroscopy (XPS), the surface

compositional mapping on the micrometer scale and

the effects due to the overlapping layers of different

materials are analyzed, through the depth profile

analysis. The study of compositional and structural

properties of thin films of SRO (Silicon Rich Oxide)

and silicon oxy-nitride devices for applications in

power MOSFETs and thin-film photovoltaic converters

was recently approached [8].

Collaborations: ANM Research, C.S.R.A.F.A,

Messina.


TECHNIQUES

Instrumentation: Raman spectroscopy system.

Back-scattering configuration, laser sources: multi-line

Argon, diode pumped Nd:YAG (second harmonic),

He-Ne. Analyzer: flat field Triax 320 monochromator

coupled with a BX 40 Olympus microscope and

equipped with gratings of 1800 and 600 lines / mm

holographic filter to eliminate the elastic scattering

component. Detector: Diode matrix CCD 1024 × 128,

cooled with liquid nitrogen. Mapping micrometer with

lateral resolution 1X1 (2 μm) using automated XY

translation. Setup for measurements on colloidal

solutions using a 10X lens focal length.

Non-linear optical spectroscopy (Z-scan technique).

Measurement system in the open and closed

configuration of a pulsed laser beam transmission

(Nd:YAG, 5 nsec), focused by a radiometric system

with two sensors and the scanning engine of the sample

along the optical axis.

Research activity: physical-chemical

characterization of bonding structures of materials in

the form of thin films and colloidal solutions of

nanoparticles: thin films of SRO (Silicon Rich Oxide),

silicon-carbon alloys and carbon-based nanostructured

systems, colloidal solutions of nanoparticles of metallic

oxides and metallic nanoparticles for applications

SERS (Surface Enhanced Raman Spectroscopy).

Analysis of nonlinear optical response of colloidal

systems of nanoparticles-based carbon and silicon:

study of the absorption coefficient and refractive index

as a function of laser pulse repetition rate,

concentration and solvent.


Messina.

Laboratory of nanomaterials

http://www.consorzio.cometa.it/

http://www.pi2s2.it/


59

Instrumentation: Nd-YAG laser pulse until the

fourth harmonic (266 nm), power adjustable up to 180

mJ (second harmonic), pulse duration 5 ns, repetition

up to 20 Hz, optical beam focusing, handling and

control of the metal target submerged in liquid (system

for laser ablation in liquids). System for spraying

deposition of thin layers of colloidal solutions: the

technique of spraying by automated airbrush is a

methodology used for the transfer of nanoparticles in

colloidal phase on surfaces of various kinds (even

flexible). The system consists of a compressed gas

atomizer with interchangeable nozzles of various sizes.

The nozzle is placed on a medium which ensures a

movement for a uniform distribution of nanoparticles

on the surface to be coated. The jet is directed into a

deposition chamber that houses a sample holder heated

to a temperature higher than the evaporation of the

solvent. A system for the removal of moisture in the

deposition chamber is also provided.

Research activity: synthesis, laser ablation in

liquids, and characterization of nanostructured metal

oxides for the production of gas sensors and

applications of metal nanoparticles for SERS (Surface

Enhanced Raman Spectroscopy).


Messina.

LABORATORY OF OPTICAL SPECTROSCOPY

Instrumentation: PE 750 UV-Vis-Nir Perkin Elmer

(200 – 3300 nm), Lambda 2 UV-VIS-Nir Perkin-Elmer

(200 – 1100 nm), FT-IR (Spectrum 100) Perkin Elmer

(7800-370 cm-1

) spectrophotometers; FluoroMax – 2

Jobin Ivon (200-900 nm) spectrophotofluorimeter;

optical microscope.

Research activity: optical spectrophotometry (UV-

VIS-NIR). Measurements of absorption of

electromagnetic radiation in the UV-VIS range allow

to make a qualitative analysis of a given material. The

profile of an absorption spectrum depends on various

parameters such as the chemical and aggregation state

of the analyzed sample. In addition, the absorption at a

given wavelength depends on the nature and

concentration of the analyte [9].

Collaborations: ST Microelectronics, Catania, CNR

Messina, RIS Messina.


ANALYSES

Instrumentation: System for dielectric and

electrical transport measurements (RLC HP4284A

shunt, RMC LTS-LN2-VT cryostat, vacuum system (~

10-6

torr), temperature control device Lake Shore 330,

Keithley 236 unit, pc).

Research activity: study of electrical transport and

dielectric properties of organic-inorganic hybrid

multifunctional materials films and powders consisting

of intercalation (nanocomposite) prepared by our

research group. The electronic properties of these

materials are also studied, using the photoelectronic

spectrometer, dual anode Mg/Al K and the optical

properties by means of spectrophotometers available in

the laboratory of optical spectroscopy [10].

Collaborations: IPCF-CNR Messina, CNR Napoli.

Conclusions

During the last five years a number of twenty PhD in

physics were formed at the Messina University.

The experience accumulated during the years of

doctoral and skills acquired allow them to aspire to

scientific careers in universities, institutes of higher

education, in research institutions and national (CNR,

INFN, ENEA, ENI, etc..) and International

Laboratories, with a special screening in Europe. The

professionalism of a PhD doctor allows also the

inclusion in any facility operating in areas requiring

advanced professional skills through computer

programming and simulation models of complex

processes and teaching in secondary schools of

physics, mathematics, electronic and information

technology.

References

[1] L. Torrisi, F. Caridi, L. Giuffrida, Nucl. Instr. And

Meth. B, 268 (2010) 2285-2291;

[2] A. Mandanici; M. Cutroni, R. Rickert, Journal of

Non-Crystalline Solids, 357 (2) 264-266 (2011);

[3] S. Magazù, F. Migliardo, A. Benedetto, The

Journal of Physical Chemistry B, 115 (24) 7736-

7743 (2011);

[4] A.K. Nasirov, G. Mandaglio, M. Manganaro, A.I.

Muminov, G. Fazio, G. Giardina, Physics Letters

B, 686 (1) 72-77 (2010);

[5] G. Barone, V. Crupi, F. Longo, D. Majolino, P.

Mazzoleni, V. Venuti, Journal of Molecular

Structure, 993 (1-3) (2011);

[6] Auditore L., Barna R.C., Emanuele U., Loria D.,

Trifiro A., Trimarchi M., Nucl. Instr. and Meth. B,

266 (10) 2138-2141 (2008);

[7] G. Carini, G. Tripodo, L. Borjesson, Materials

Science & Engineering A, 521-522 247-250 (2009);

[8] E. Fazio, F. Neri, S. Patanè, L. D‘Urso, G.

Compagnini, Carbon, 49 (1) 306-310 (2011);

[9] A.M. Mezzasalma, G. Mondio, T. Serafino, F.

Caridi, L. Torrisi, Appl. Surf. Sci., 255 (7) 4123-

4128 (2009);

[10] L. Silipigni, L. Schirò, L. Monsù Scolaro, G. De

Luca, G. Salvato, Appl. Surf. Sci., 257 (24) 10888-

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http://periodici.caspur.it/search_results.php?query=author:Caridi%20author:F.&query_stampa=Caridi%20F.&date_past=none&rows=10

http://periodici.caspur.it/search_results.php?query=author:Silipigni%20author:L.&query_stampa=Silipigni%20L.&date_past=none&rows=10

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60


61

ENHANCED OPTICAL FIELDS FOR AGGREGATION OF METAL

NANOANTENNAS AND LABEL FREE HIGHLY SENSITIVE DETECTION

OF BIOMOLECULES

B. Fazio

a,*, C. D‘Andrea

a,b, V. Villari

a, N. Micali

a, O. Maragò

a, G. Calogero

a and P.G. Gucciardi

a

a) CNR – Istituto Processi Chimico-Fisici, viale F. Stagno D’Alcontres 37, 98158 Messina, Italy


b)Dottorato in Fisica dell’Università di Messina, Dip.to di Fisica della Materia e Ingegneria Elettronica,

viale F. Stagno D’Alcontres, 98158 S. Agata-Messina, Italy

Abstract

Aggregated metal nanostructures are characterized by

strongly intense electromagnetic fields localized in the

cavities region, referred as ―hot spots‖, allowing for

high sensitive vibrational spectroscopy. We report on

the implementation of a laser induced Surface-

Enhanced Raman Scattering sensor in liquid

environment by controlled aggregation of gold

nanorods dispersed in solution obtained through an

interplay between thermal and radiation pressure

effects. The creation of highly efficient hot spot

regions enables the Raman detection of proteins

dissolved in buffer solution at low concentration (down

to 10-7

M) with an estimated enhancement factor of

105. This methodology paves the way to a new

generation lab-on-chip sensors that implies user-

friendly experimental set up allowing for highly

sensitive vibrational spectroscopy of biomolecules in

their natural habitat and getting over the drawback of

the standard methods based on the difficulty to

manipulate metal nanostructures or realize active

substrates that experience a highly efficient SERS.

Introduction

The discovery of Surface-Enhanced Raman

Scattering (SERS) phenomena and single molecule

sensitivity [1-5], due to the unique electronic and

optical properties of metal nanoparticles, opened the

doors to promising applications in material science and

optical biosensors.

SERS from isolated metal nanostructures is usually

much weaker compared to what is observed on

aggregates due to the strong field enhancement

occurring in the gap regions (hot spots) between

adjacent nanoobjects [2-5]. A controlled creation of hot

spots in liquid, the natural habitat of biomolecules, is a

challenge in which optical forces play an important

role. Optical trapping (OT), manipulation and

deposition of metal nanostructures, gold and silver,

has been at the center of an intense research [6-9].

Here we show how the simultaneous occurrence of

optical, mechanical and thermal effects, promotes

aggregation of already formed gold nanorods staying in

a colloidal suspension with the consequent creation of

hot spot regions where biomolecules experience high

field enhancement fundamental for their label free

detection at submicromolar concentration. We validate

the SERS biosensor efficiency by detecting

biomolecules as Bovine Serum Albumin (BSA),

Phenylalanine (Phe), Lysozyme (Lyz) and a protein not

yet well known from a spectroscopical point of view,

but of a great biomedical interest, the Manganese

Superoxide Dismutase (MnSOD). Indeed, the MnSOD

is considered a valid pathological biomarker, due to its

levels in the plasma that are significantly higher in

patients with ovarian carcinoma.

Materials and methods

Materials. Commercial gold nanorods (35x90 nm) are

purchased from Nanopartz. They come in a DI water at

a concentration of 0.05 mg/ml; the solution contains

<0.1% ascorbic acid and <0.1%

Cetyltrimethylammonium bromide (CTAB) surfactant

capping preventing spontaneous re-aggregation, and

have a positive -potential (+40 mV). The Bovine

Serum Albumin buffered solutions at various

concentrations (in the range between 10-3

M and 10-

7M) are prepared by mixing the suitable amount of

BSA lyophilized powder (Sigma-Aldrich) with a 200

mM of Phosphate Buffer Solution (pH 7.2) obtained

with Na2HPO4(14.94 g) and NaH2PO4 (5,063 g)

dissolved in 200mL of DIwater. Then, the gold

nanorods solution is added to the prepared mixture

with a ratio of 1:7 v/v. An amount of 75 l of BSA

and NRs solution was put inside a typical glass cell

used for optical trapping experiments. Following the

same procedures we prepared analogous solutions

containing gold nanorods and, respectively, Lyz at 10-

6M, MnSOD at 10

-4M and Phe at 10

-3M in PBS.

Setup. We performed the SERS experiment using a

Raman Micro-Spectrometer (LabRam HR800 - Horiba

Jobin Yvon) coupled to the 632.8 nm line of a He-Ne

laser; the beam (P = 6.3 mW) was focused on a 500 nm

diameter spot in the liquid, close to the bottom of the



62

cell, by a 100X microscope objective (Olympus,

NA=0.95) a droplet of the BSA and NRs solution is put

inside a glass cell (a model typically used for optical

trapping experiments) and placed under a Raman

Micro-Spectrometer (LabRam HR800 - Horiba Jobin

Yvon) coupled to the 632.8 nm line of a He-Ne laser.

The spectrometer was equipped with a Peltier cooled

CCD array (HJY-Synapse) as detector. The instrument

was also employed to collect the extinction spectrum of

the aggregate of gold NRs, by using a Xe lamp as

white light source.

Figure 1: (a) Sketch of the experiment and of the

formed aggregate. (b) Absorption spectrum of the gold

nanorods solution (blue line) compared to the

extinction spectrum of the photo-induced aggregate

(brown line).

Results and discussion

By manually changing the fine focus inside the

solution and setting it at the bottom of the cell close to

the rim, the intercepted gold nanorods are mechanically

constrained in a confined region; the aggregation

process is activated in some seconds; in figure 1.a a

sketch of the experimental configuration and the

aggregate formation. Due to the slightly blue shifted

excitation with respect to their LSP resonance, the gold

nanorods are subjected to both a scattering force and a

repulsive gradient force, so that they are not trapped in

the laser focus but rather strongly pushed towards the

bottom of the sample cell along the optical axis. On

the cell surface they aggregate for photoinduced

thermal effect [9,10].

The extinction spectrum of the formed aggregate

(figure 1,b), captured in situ, shows a broad band

extinction feature, ranging between 420 and 900 nm

and peaked at 770 nm, that dominates; it is suitable to

underline that the 632.8 nm of laser source, used as

SERS probe, falls whithin the localized surface

plasmon resonance of the aggregate, while it falls

outside of the single rods plasmonic absorption

features (figure 1,b blue line) at λLSP = 687 nm and λLSP

= 527 nm, along their long and short axes respectively

[11].

The relatively high energy density (~ 25 mW/µm2) in

the focal spot and the quasi resonant laser excitation of

the LSPs modes causes a not negligible light

absorption by the NPs which is partially converted into

heat. By Stokes/Anti-Stokes Raman measurements we

have estimated a temperature of about 60°C in the

irradiated zone after 10 minutes of laser focusing. At

this temperatures thermally induced structural

rearrangement of gold nanorods in micelles capping

has been observed [12].

Depolarized Light Scattering (DLS) measurements,

here not shown, confirm that a thermal re-organization

of the rods into small clusters takes place in the

investigated solution at temperature as low as 60°C.

Indeed, the mean hydrodynamic radius of about 65 nm,

detected at room temperature and due to gold rods with

a shell of BSA, likely stabilized by electrostatic

interaction between the positively charged capping

agent of the rods and the negative charge of BSA,

becomes 100 nm for the gold/BSA aggregates at 60°C.

Figure 2: (a) SERS of buffered BSA molecules at 0.1

mM (black line), 1 M (red line) and 0.1 M (blue

line) . (b) Raman spectrum of buffered BSA solution at

0.1 mM without nanorods induced aggregation.

This increment of the mean size is due to thermal

aggregation between gold rods mediated by BSA, that

at this temperature is known to form small oligomers.


63

In figure 2 is shown the strong SERS signal of BSA

molecules staying in the aggregates proximity,

compared to the Raman signal of the same solution in

absence of aggregates formation. We estimated a SERS

enhancement factor of 2x105 by the ratio between the

intensity of the SERS feature of the phenylalanine ring

breathing at 1004 cm-1

obtained for the buffered

solution of BSA at concentration of 10-7

M and the

same Raman feature collected for a buffered solution

of BSA 10-3

M without gold nanorods addition. BSA at

10-3

M corresponds to the concentration limit for the

Raman detection in our experiment.

Under the same experimental conditions (time=10s, 4

accumulations, after a NRs aggregation time of 30s)

the intensities of the SERS spectra are not depending

on the BSA concentration. This occurrence confirms

that what we reveal is SERS from hot spot region and

suggests us that tenths of micromolar concentration of

protein is not a detection limit for our experiment.

However, when a concentration of 10-8

M of BSA in

PBS solution is added to the same concentration of

NRs solution previously used, not stable aggregates are

formed and we hardly collect only SERS spectra of

the CTAB surfactant.

In this latter case any BSA mediation and stabilization

process occurs for aggregates formation, owing to the

protein negligible amount that don‘t saturate the rods

quantity; as a consequence, only a transient NRs

aggregation due to the optical forces is experienced and

immediately disrupted by the repulsive electrostatic

action of the surfactant layer.

The temporal dynamics of the photothermal creation of

the hot spots can be followed by acquiring consecutive

SERS spectra (figure 3a) and monitoring the temporal

increase of the intensity of the protein spectral

signatures. We observe a preferential increment of the

features attributed to the aromatic residues in the

structure (Phe, Tyr, Trp), due to the intercalation of the

hydrophobic side chain into the CTAB layer. The high

enhancement of the 1395cm-1

COO-symmetric

stretching is due to the strong electrostatic interaction

with the surfactant bilayer. A similar behavior has been

observed by Kaminska and coworker in the interaction

between bovine pancreatic trypsin inhibitor (BPTI) and

CTAB-protected gold nanoparticles deposited on

functionalized silicon surface [13,14].

Figure 3: Consecutive SERS spectra of BSA in PBS

solution and gold nanorods (a). Trend vs time of some

protein spectral features (b).

The functionality of the SERS biosensor obtained by

photoinduced aggregation of gold nanorods has been

validated for many molecules of biological interest. In

figure 4.a,b,c the SERS spectra of lysozyme protein,

Phenylalanine amminoacid and Manganese Superoxide

Dismutase, compared to the Raman signal of the

respective powders are shown [15].


64

Figure 4: SERS of buffered biomolecules solutions

(blue lines) compared to Raman spectra of the

respective powder and to the Raman spectra of the

same solution in absence of gold aggregates: (a)

Lysozyme in PBS at 1 M, (b) Phenylalanine in PBS at

1 mM and (c) Manganese Superoxide Dismutase at

0.1 mM.

Conclusions

In summary, we implemented a SERS biosensor based

on photothermally aggregated gold nanorods, operating

in liquid environment. This in situ aggregation process

has been applied for the Raman detection of Bovine

Serum Albumin (BSA) molecules in Phosphate Buffer

Solution (PBS) at concentration down to 10-7

M. The

method has been successfully validated for the SERS

detection other molecules of biological interest in their

natural habitat, as Phe, Lyz and MnSOD, the latter

being a precious biomarker in medical diagnosis.

Acknowledgments

We acknowledge funding from the EU-FP7-

NANOANTENNA project GA 241818 ―Development

of a high sensitive and specific nanobiosensor based on

surface enhanced vibrational spectroscopy‖ and the

PRIN 2008 project 2008J858Y7_004 ―Plasmonics in

self-assembled nanoparticles / Surface Enhanced

Raman Spectroscopy on self-assembled metallic

nanoparticles.‖

References

[1] M. Moskovitz, Rev. Mod.Phys. 1985, 57, 783.

[2] S. Nie and S. R. Emory, Science 275 (1997) 1102.

[3] K. Kneipp et al., Chemical Physics 247 (1999) 155. [4] K. Kneipp, M. Moskovits and H. Kneipp, Surface Enhanced

Raman Scattering; Springer: New York, 2006.

[5] E. Le Ru, P. Etchegoin, Principles of Surface Enhanced

Raman Spectroscopy; Elsevier: Amsterdam, 2009.

[6] F.Svedberg et al., Nano Lett., 6 (2006) 2639.

[7] F. Svedberg et al., Faraday Discuss., 132 (2006) 35

[8] L. Tong, Lab Chip, 9 ( 2009) 193. [9] M. J. Guffey and N. F. Scherer, Nano Lett., 10 (2010) 4302

[10] M. J. Guffey and N. F. Scherer, Proc. of SPIE, Optical

Trapping and Optical Micromanipulation VII, edited by Kishan Dholakia, Gabriel C. Spalding (2010) Vol. 7762.

[11] P. H. Jones et al., ACS Nano 3 (2009) 3077.

[12] M.B. Mohamed, J. Phys. Chem B., 102 (1998) 9370 [13] A. Kaminska et al., Phys Chem Chem Phys 10 (2008) 4172.

[14] A. Kaminska et al., Journal Raman Spect 41 (2009) 130.

[15] B. Fazio, C. D‘Andrea, V. Villari, N. Micali, O. Maragò, M.A. Iatì, G. Calogero, P.G. Gucciardi, in preparation.


65

MISSING RESONANCES AT THE BGO-OD EXPERIMENT

F. Curciarelloa,b,*

, V. De Leoa,b

, G. Mandaglioa,b

, M. Romaniuka,b,c

, G. Giardinaa,b

a)Dipartimento di Fisica, Università di Messina, I-98166, Messina, Italy

b) INFN-Sezione Catania, I-95123 ,Catania , Italy

c)Institute for Nuclear Research, National Academy of Science of Ukraine, Kiev, 03680, Ukraine

*Corresponding author, e-mail: [email protected]

Abstract

The excited states of nucleons are mostly treated in

the framework of the so-called ―constituent quark

model‖. This model has been very successful in

describing mesons and baryons into the well known

multiplet structures and in the prediction of the

hadronic excitation spectrum by few parameters.

However there are some problems concerning the

description of the observed baryon resonance spectrum

by the constituent quark model. One problem is due to

the so-called ―missing resonances‖: much more excited

states of the nucleon are predicted by the model than

the ones have been observed in experiments. It is

unknown if this mismatch is caused by experimental

limits or by the models used to describe the nature of

quarks bonds inside nucleons. Indeed the choice of the

theoretical model is of basic importance to fix the

effective degrees of freedom of the constituent quarks

and therefore the number of possible excited states of

nucleon. For this reason other quark models have been

proposed as the ―di-quark‖ model and the ―flux-tubes‖

model. The only way to establish the proper effective

degrees of freedom is to test the theoretical predictions

with experiment[1-2-3]. In the present paper will be

presented the specific program of the BGO-OD

experiment at ELSA of Bonn in the missing resonances

research. The international experiment BGO-OD

(INFN-MAMBO experiment) consists of a 4π-

electromagnetic calorimeter, different charged sensible

detectors for tracking particles, an open dipole

spectrometer for charged particles and momentum

reconstruction.

That experiment, thanks to the high photon

luminosity (107s) of energy up to 3.2 GeV produced by

electron bremsstrahlung of the ELSA cyclotron,

represents a new experimental information source

devoted to investigation of the ―missing resonances‖

puzzle.

Introduction

The availability over the last decade of high duty-

cycle accelerators coupled with the use of large solid-

angle detectors yielded a wealth of experimental

information in the field of the photo- and

electroproduction of mesons from the nucleons. The

attempt is to extract, from photoproduction, the

electromagnetic couplings and furthermore the

hadronic properties of the excited nucleon states that

cannot be accessed via pion scattering, either because

the resonances largely overlap, or because of a weak

coupling to the single pion-nucleon channel. The

energy scale which is typical of the nucleon and its

resonances is the low energy regime where a

perturbative approach of the QCD theory is not

possible because of the strong coupling constant

becomes large. This situation offers both a challenge

and a chance: we do want to understand the physics

laws governing the bilding blocks of the matter at low

energies, in the regime where we encounter them in the

nature, on the other hands is obvious that the complex

many-body system ―nucleon‖ offers the ideal testing

ground for concepts of the strong interaction in the

non-perturbative regime. Therefore the most important

step toward the understanding of the nucleon structure

is the identification of the effective degrees of freedom

which naturally must reflect the internal symmetries of

the underlying fundamental interaction.

This step is attempted in the framework of the

constituent quark model[4-5-6] which have

contributed

Fig. 1 Effective degrees of freedom in quark

models: three equivalent constituent quarks,

quark-diquark structure, quark and flux tubes

substantially to our understanding of the strong

interaction.

The classification of the mesons and baryons in the

well known multiplet structures as derived from the

symmetry, and the description of the hadronic

excitation spectrum with only few fitting parameters

were striking success of this model. Most of the models

start from three equivalent constituent quarks in a

collective potential . Here the quarks are not point-like

but have electric and strong form factors. The potential

is generated by a confining interaction, for example in


66

the flux tubes picture, and the quarks interact via a

short range residual interaction. This fine-structure

interaction, usually taken as color magnetic dipole-

dipole interaction mediated via one-gluon-exchange

(OGE) is responsible for the spin-spin and spin-orbit

terms. However, alternative models were developed.

Indeed, models have been proposed that are based on a

different number of degrees of freedom (see fig.1). One

group of models describes the nucleon structure in term

of a quark-diquark (q-q2) cluster[7], if the diquark is

sufficiently strongly bound, low lying excitations of the

nucleon will not include excitation of the diquark.

Therefore, these models predict a fewer low-lying

states of the nucleon than the conventional quark

models. On the other hand other models predict an

increased number of excitation states with respect the

usual constituent quark model[8-9]. The choice of the

theoretical model to describe nucleon structure is of

crucial importance because the number of excited

states with defined quantum number (baryon

resonances) follows directly from the number of

effective degrees of freedom of quarks inside nucleon.

Consequently a comparison of the experimentally

excitation spectrum to model predictions can allow us

to determine the correct number of degrees of freedom

and so to understand the nature of quark bonds and its

interaction inside the nucleon. However, from an

experimental point of view the situation is quite

different from atomic and nuclear physic. The

dominant decay channel of a nucleon resonance is the

hadronic decay via emission of mesons (see fig. 2) .

Thus, the lifetimes of the excited states are typical of

the strong interaction (η~10-24

s) with corresponding

widths of few 100 MeV. The spacing of the resonances

is often no more than a few 10 MeV so the overlap is

very large, this makes difficult to identify and

investigate individual states.

Fig.2 Representation of a photoproduction of

meson through an intermediate state of nucleon

resonance of defined isospin I and angular

momentum J.

The most widely used reactions for the study of

nucleon resonances use beams of long-lived mesons.

However the exclusive use of pion induced reactions

would bias the data base for resonances coupling

weakly to the Nπ channel. Indeed, a comparison of

excitation spectrum predicted by modern quark models

to experimentally established set of nucleon resonances

results in the problem of ―missing resonances‖: many

more states are predicted than have been observed. It

is unknown if this evidence is related to an inept

determination of effective degrees-of-freedom in the

theoretical models or if it is an experimental limit. One

hypothesis of this mismatch is the decoupling of many

resonances from the partial wave analysis of pion

scattering. This resonances can be found when other

initial and/or final states are investigated. In fact, recent

quark models predict a number of unobserved

resonances to have large decay branching ratios for the

emission of mesons other than pions. To observe this

states, nucleon should be excited by scattering of

respective mesons. However, most of them are short

lived so the preparation of secondary beams becomes

impossible. The use of induced reactions by

electromagnetic interaction offers an alternative. The

progress made in accelerator and detector technology

during the last fifteen years has considerably enhanced

our possibility to investigate the nucleon with different

probes. In particular, the new generation of electron

accelerators, like ELSA in Bonn, are equipped with

tagged photon facilities and state-of-art detector

systems.

Fig.3 Overview of the ELSA facility in Bonn

which produce a photon beam up to 3.2 GeV

with the bremsstrahlung technique.

At ELSA facility the tagged high energy photon

beam is produced through the bremsstrahlung

technique: electron beam from accelerator impinges

on a radiator, scattered electrons produce

bremsstrahlung with the typical spectral distribution

1/Eγ, with energy up to 3.2 GeV. The purpose of the

experiment is to study a wide class of reactions

induced by photons on nucleons and nuclei with

production of pseudoscalar mesons (π0,η),

pseudovettorial mesons (ω, ρ, θ) and the precise

determination of the properties of baryonic resonances,

in the energy region from threshold to 3.5 GeV using a

polarized gamma-ray beam and/or polarized targets.


67

The activities will be held in Bonn in the B1project[10]

at the Physikalischen Institute of the Rheinischen

Friedrich Wilhems-Universität. The involved groups

and organisations are coming from Russia, Ukraine,

Italy and Germany. First data taking is scheduled for

the biginning of the next year.

BGO-OD experimental set-up

A schematic view of the experimental apparatus

installed in the beamline S-Bonn[11] is shown in fig.

4. The experimental setup is a combination of an open-

dipole forward spectrometer optimized for the

detection of charged particles and of a large solid angle

(25-155 degrees) detector, the BGO crystal ball, that

covers the central angular region and is optimized to

detect neutral particles. This particular set-up

configuration is well designed to allow the

investigation of photoproduction reactions and

discrimination of multi-particle final states with

different charges. Dipole field together with multiple

tracking sections allows for momentum/charge analysis

of reaction products not possible in previously

experiments.

The polar angular region of small angles, θ<12°, is

covered by B1 magnetic spectrometer that produces a

dipolar field of about 0.5 T and that will be used for the

separation, identification and reconstruction of the

momentum (resolution 0.5%) of charged particles

emitted in the photoproduction process . For this

purpose, the spectrometer is equipped with:

a first track scintillating fibers detector (MOMO

detector in fig.4) made of 672 fibers arranged on 3

layers, which allow to have a spatial resolution of 1,5

mm;

an aerogel Cĕrenkov detector for the discrimination

of charged pions from protons and particulary from

charged kaons in the 600-1500 MeV/c range;

a second track scintillating fibers detector (SciFi2)

that consists of 640 scintillating fibers arranged in 4

circular layers;

two set of double plane drift chambers for particle

tracking, placed at the exit of the dipole;

a time-of-flight detector (TOF) which provides time

flight measurements for charged particles and neutrons.

The central region is covered by:

the BGO, (Bi4Ge3O12), an homogeneous

electromagnetic calorimeter made of 480 truncated

pyramidal crystals placed inside 24 carbon fiber

baskets each one containing 20 crystals and supported

by an external steel structure. Each crystal is 24 cm

long (21 radiation lenghts) and provides an high energy

resolution for photon detection ( ≈ 3% FWMH at

1GeV) a good response for proton with energy up to

400 MeV and a good neutron detection efficiency. The

angular resolution is of about 6-8 degrees. The

characteristics of the response time of the calorimeter

allow to use the signal for the experimental trigger.

Each crystal is coupled to one phototube for the read

out of the signals. The detector is property of INFN

and used in the GRAAL experiment closed at the end

of 2008;

a crystal barrel detector, made of 32 plastic

scintillator bars, which allows, through

measurement of ΔE, the discrimination between

charged and neutral particles and,

in combination with the information of energy released

in the calorimeter, the identification of charged

particles (protons and pions);

multi wire proportional chambers (MWPC's) for

inner tracking;

multi resistive proportional chambers (MRPC's) for

forward tracking;

target of H2 or deuterium that is tight enclosed by

the BGO.

Fig.4 Overview of BGO-OD experimental set-

up at the beam line S

Physical program

The principle aim of this experiment is the

systematic investigation of the photoproduction of

mesons off the nucleon. These processes are related to

the structure of both, the mesons and baryons

involved, whose nature of strong bonds must still be

considered as poorly understood. Only such improved

experiments will shed new light on the low-energy

hadronic aspects of the strong interaction. Polarisation

measurements are indispensable to characterize the

relevant degrees of freedom in the production process

of the different mesons, in particular the formation and

role of the missing resonances. Therefore, meson

photoproduction provides an ideal tool to investigate

particular baryonic states which challenge the quark

model through their unusual features. The


68

photoproduction of mesons off the nucleon provides

also access to several aspects of low-energy strong

interaction. The mechanisms involved are not clear, in

many cases not even the relevant degrees of freedom,

from which resonance spectra depend. Of particular

interest are the excitation and subsequent decay of

baryon resonances, as well as intermediate particle

exchanges in the production process, especially

important in vector-meson production. To achieve one

of the central goals of low-energy hadron physics, to

disentangle and understand the complicated nucleon

resonance spectrum, a better understanding of the

meson production mechanisms is an indispensable

prerequisite. It is also the basis to understand the

features and hence the structure of individual states

which in a striking manner do not fit to the description

of quark models. Open problems are: (i) the

mechanism and the relevant degrees of freedom in the

photoproduction of mesons, (ii) the contrast between

the general spectroscopic success of quark models and

the vast discrepancy between expected and observed

number of states, (iii) the structure of some well

established resonances which is still not well

understood.

In order to try to solve these problems, processes

beyond single pion photoproduction must be

investigated. Final states that involve multiple pions, η,

η', K, K*, ω and θ mesons, or combinations thereof (it

should be stressed that some of this mesons have

masses bigger than photon beam maximum energy). It

is clear that progress in this field means approaching to

an understanding of the complex nature of the deepest

bonds of matter known so far.

Experimentally, the new B1 magnetic spectrometer

will provide high resolution and good particle

identification for charged final states, in particular for

K±. Since the acceptance of the spectrometer extends to

almost 0-degree forward direction, it is ideally suited to

investigate θ production through simultaneous K+ and

K- detection. Moreover, the high resolution detection of

recoil protons may not only add to our understanding

of the basic production process, but also favour

precision measurements regarding the in-medium

properties of the ω meson. Finally, combination of the

crystal calorimeter and the forward spectrometer yields

a unique instrument for complicated multi-particle final

states and in this way gives us access to the study of a

wide range of phenomena in particle physic.

BGO CALIBRATION-EQUALIZATION

In this paragraph we report an overview on the

calibration-equalization operations performed on the

BGO calorimeter crystals.

We performed not a simple calibration of BGO

crystals but, more important, we also made an

equalization of crystals varying high voltage applied to

phototubes to homogenize their response.

The operations can be performed by remote and still

continuing now in Messina.

Fig.5 Scheme of the experimental calibration

chain

In fig.5 we can see a roughly representation of the

experimental chain of calibration: the output signal

from the phototube, coupled to the crystal, is sent to a

mixer reducing its amplitude and then reaches the

ADC module for the readout. We worked on the

calibration of 64 crystals at time of the 480 crystals

(four ADC available for acquisition with 16 channel

each one, in future with a full equipped BGO

elettronics, we will have 30 ADC to acquire

simultaneously signal from the 480 crystals). For the

calibration we used three sources of 22Na, located

inside the BGO cylindrical hole, which is characterized

by two emission peaks: the first at 0.511 MeV and the

second at 1.275 MeV. In order to derive the calibration

constants for each channel, we tried to fix the energy of

the second peak at the channel 480 of the ADCs, we

also made an equalization of the crystals by changing

the high voltage applied to the fototubes in order to

obtain the response, (calibration peak), at the same

channel of ADC for all crystals.

The calibration constant is about 0.021 MeV/

channel. The peaks have also been monitored in time

and the fluctuations of the position of the second peak,

due to the fitting procedure and to the response of

crystal+ADC to the source, is of about 1-2 channels

corresponding to about 0.021-0.042 MeV. This means

an incertitude of about 1,6%-3,2% of the energy. The

intrinsic resolution of the BGO+ADC at 1.275 MeV is

about 25%-30%.


69

Fig.6 Example of signal acquisition

BIBLIOGRAPHY

[1] A. Fantini et al. Phys. Rev. C 78, 015203(2008); [2] R. Di Salvo et al. Eur. Phys. J A 42,151 (2009);

[3] G. Mandaglio et al. Phys. Rev. C 82, 045209 (2010);

[4] M. Gell-Mann, Phys. Lett. 8 (1964) 214; [5] O.W. Greenberg, Phys. Rev. Mt. 13 (1964) 598;

[6] R.H. Dalitz, Proceedings of the XII Int. Conf. On High Energy

Physics Berkeley, Calif. (1966); [7] M. Anselmino et al., Rev. Mod. Phys. 65 (1993) 1199;

[8] R. Bijker, F. Iachello, A. Leviatan, Ann. Phys. 236 (1994) 69;

[9] R. Bijker, F. Iachello, and A. Leviatan, Phys. Rev. D 55 (1997) 28;

[10] http://b1.physik.uni-bonn.de/;

[11] http://b1.physik.uni-bonn.de/ExperimentalSetup.

http://b1.physik.uni-bonn.de/

http://b1.physik.uni-bonn.de/ExperimentalSetup


70


71

RESONANT LASER ABSORPTION AND SELF-FOCUSING EFFECTS

PRODUCING PROTON DRIVEN ACCELERATION FROM

HYDROGENATED STRUCTURES

M. Cutroneo1,2

and L. Torrisi1

1Dottorato di Ricerca in Fisica, Università di Messina, V.le F. Stagno D’Alcontres 31, 98166 S. Agata (ME), Italy

2Centro Siciliano di Fisica Nucleare e Strutt. della Materia, V.le A. Doria 6, 95125 Catania , Italy


Abstract

Resonant laser absorption and self-focusing effects

were investigated as two typical non-linear processes

occurring inside laser generated non-equilibrium

plasmas.

The ion emission in laser-generated plasma is dealt

at low and high intensities from 1010

W/cm2 up to

values higher than 1016

W/cm2. The properties of

plasma are strongly dependent on the time and space,

laser parameters (intensity, wavelength, pulse duration,

spot dimension, focal position…), target composition

(polymers, metals, ceramics) and target geometry

(thickness, spot/thickness ratio, surface curvature,…).

A considerable interest concerns the energetic and

intense proton generation for the multiplicity use that

proton beams have in different scientific fields

(Nuclear Physics, Astrophysics, Bio-Medicine,

Microelectronics, Chemistry,…).

Measurements have been performed at INFN-LNS in

Catania and at PALS Laboratory in Prague, by using

low and high laser pulse intensities, respectively. Thick

and thin targets and different detection techniques of

ion analysis have been employed.

The mechanisms of resonant absorption of the laser

light, produced in specific targets containing

nanostructures with dimensions comparable with the

wavelength and high electron density, enhances the

proton yield and the proton kinetic energy as result of

resonant absorption effects.

The mechanisms of self-focusing, obtained by

changing the laser focal distance from the target

surface, increase the local intensity due to further

focalization the laser light in the dense vapour and

consequently the plasma temperature, the density and

Coulomb ion acceleration. Real-time ion detections

were carried out through Thomson parabola

spectrometer (TPS) coupled to a multi-channel-plate

(MCP). Ion collectors (IC), SiC detectors and ion

energy analyzer (IEA) have been also employed in

time-of-flight configuration (TOF) technique.

The energy and the amount of protons and ions

increase significantly when the two investigated non-

linear phenomena occur, as it will be discussed.

Introduction

The interaction of short laser pulses with solids has

become an important field of study because of many

applications, such as the fast ignition scheme of inertia

confinement fusion, the plasma-based particle

accelerator, coherent x/ -ray sources, etc.. For most of

these applications, the nature of the absorption process

must be determined.

The density scale length of the plasmas generated

from the target surfaces can be estimated as:

s pL c (1)

where cs is the ion sound speed and p is the laser

pulse duration [1]. For high intensities (> 1016

W/cm2)

and very short pulses (< 1 ps)) the scale length is too

short to generate sufficient absorption effects and

resonance absorption at the critical surface is suggested

to be one of the major absorption mechanisms. Some

experiments show that it plays an important role even

for plasmas with a scale length considerably shorter

than the laser wavelength 0. However many

theoretical works on resonance absorption are valid for

the case in which L > 0 [2]. At higher laser intensity

the electrons being pulled out by the ponderomotive

forces and then returned to the plasma at the interface

layer by the wave field can lead to a phenomenon like

wave breaking. Thus, the electron plasma wave is hard

to develop and vacuum heating tends to be dominant

[3].

A simple model is used to calculate the energy

absorption efficiency when a laser of short pulse length

impinges on a dielectric slab that is doped with an

impurity with a resonant line at the laser frequency. It

is found that the energy absorption efficiency is

maximized for a certain degree of doping concentration

(at a given pulse length) and also for a certain pulse

length (at a given doping concentration). Absorption

processes are generally dependent on the density scale

length.

Interaction of the laser radiation above some

threshold intensities with a plasma of defined

properties may significantly increase the charge state

and energy of the produced ions, due to a peculiar


72

effect occurring in the plasma, which focalizes further

the laser pulse (self-focusing effect) acting so as a

small vapor lens placed in front of the target surface.

Advances in laser technology have recently enabled the

observation of self-focusing in the interaction of

intense laser pulses with plasmas. Self-focusing in

plasma can occur through thermal, relativistic, and

ponderomotive effects [4]. Thermal self-focusing is

due to collisional heating of plasma exposed to

electromagnetic radiation: the rise in temperature

induces a hydrodynamic expansion, which leads to an

increase of the refraction index and further heating.

Relativistic self-focusing is caused by the mass

increase of electrons traveling at speed approaching the

speed of light, which modifies the plasma refractive

index, depending on the electromagnetic and plasma

frequencies. Ponderomotive self-focusing is caused by

the forces which push electrons away from the region

where the laser beam is more intense.

Both non-linear effects of resonant absorption and

self-focusing were investigated in order to produce

high yield of energetic proton emission from laser

irradiated targets, as will be presented and discussed.

Experimental set-up

The main experiments have been performed by using

the Nd:Yag laser of INFN-LNS in Catania and the

Iodine Asterix laser of PALS Laboratory in Prague.

The first has been employed at 1064 nm, 9 ns pulse

duration, 800 mJ maximum pulse energy, with

intensities between 108 and 10

11 W/cm

2. The second

has been employed at 1315 nm (1 ), 300 ps pulse

duration, 600 J maximum pulse energy, with intensities

between 1013

and 1016

W/cm2.

In order to generate protons, the irradiated targets

were thick and thin hydrogenated solids. Many of these

were polyethylene based (CH2-monomer) with

additions of nanostructures such as carbon-nanotubes

(CNT), of length of the order of 1 micron, and oxides

(such as Fe2O3). Other targets consisted of

hydrogenated Si, thin films of mylar covered by Au or

Al films, hydrates and metals. Generally thick films (1

mm thickness) were used at LNS for irradiation at low

laser intensities to generate backward directed plasmas,

while thin films (of the order of 1 micron in thickness)

were employed at high laser intensity at PALS in order

to generate forward directed plasmas.

Time-of-flight (TOF) measurements have been

obtained with ion collectors (IC), semiconductor

detectors based on SiC, and electrostatic deflector ion

energy analyzer (IEA) that permits to measure the

average ion energy, the ion energy and the charge state

distributions, respectively. Details on IC, SiC and IEA

detector are given in literature [5,6].

The ion plasma temperature, Ti, was measured

though the Coulomb-Boltzmann shifted (CBS) fit of

the experimental ion energy distributions given by the

IEA spectrometry [7]; the electronic plasma

temperature, ne, was measured through the evaluation

of the ablation yield (atoms removed from the laser

crater per laser shot) and the volume of the visible

plasma observed by a fast CCD camera.

A Thomson parabola spectrometer (TPS) couplet to

a multi-channel plate (MCP) was also employed at

PALS in forward direction along the normal to the

target surface in order to separate the different ions

contributions by means of magnetic deflection by using

a magnetic field of the order of 0.1 Tesla and an

electric deflection of 3 keV/cm. A scheme of the TPS

is reported in Fig. 3b. TPS measures the energy, charge

states and ion species of ejected particles from plasma

for comparison with simulation programs.

Finally, a streak camera was employed at PALS to

measure the laser focal position (FP) distance with

respect to the target surface. Negative distances mean a

focus in front of the surface while positive distances

mean a focus inside the target.

Fig 1. Typical IC spectra obtained at low intensity

relative to pure polyethylene irradiation (a) and

typical resonant absorption obtained by irradiating

CNT nanotubes, 0.1% in concentration, embedded in

polyethylene (b).


73

Results

At low intensities, of the order of 1010

W/cm2 a

typical spectrum of ions emitted from polyethylene and

detected by IC shows a large and slowly peak due to

the carbon charge states and a faster peak due to

protons, as reported in Fig. 1a.

Fig. 2: Typical proton energy distribution

relative to the ion emission from low intensity

laser irradiation of pure polyethylene (a) and

relative to that from Silicon hydrogenated

nanospheres target irradiated in the same

experimental conditions (b).

In this case the TOF distance is 60 cm, thus the

corresponding proton peak energy is about 75 eV. Pure

polyethylene shows a low absorption coefficient to

1064 nm and a low electron density. Embedding CNT

nanostructures in polyethylene the absorption

coefficient changes strongly thus the result of the ion

emission at low laser intensity, also, as reported in Fig.

1b. The SEM photo of the carbon nanotubes is reported

in the inset of the figure. In this case the TOF length

was 150 cm thus the corresponding maximum proton

energy, calculated at the FWHM of the proton peak, is

about 120 eV. The comparison between the two spectra

shows that the proton/carbon ratio increases from 0.05

in pure polyethylene up to 1.5 for 0.1% concentration

of CNT. Thus the insertion of absorbent

nanostructures, with length comparable with the laser

wavelength, produces effects of resonant absorption

that can be responsible of the strong increment of the

proton yield emission while a negligible proton kinetic

energy increment is recorded. However, significant

increment of the proton energy can be obtained using

other special nanostructures inducing resonant

absorption effects.

At low laser intensity, a typical energy distribution

of the protons emitted from an irradiated polyethylene

target is reported in Fig. 2a. It gives average proton

energy of about 100 eV. For comparison, the proton

energy distribution obtained by irradiating amorphous

surface layers of hydrogenated silicon (Si:H) with 100

nm diameter nanospheres is reported in Fig. 2b. The

SEM photo of the nanospheres is reported in the inset

of the figure. It gives maximum proton energy above

1.5 keV. This result may be due to a strong resonant

effect generated by the high electron density of the first

layers of the high absorbent target.

At high intensity, of the order of 1016

W/cm2, the

produced plasma show high electron densities and the

resonant absorption effects becomes more probable. A

typical spectrum of ions emitted from CNT nanotubes

embedded in PMMA target is provided by the

Thomson Parabola spectrometer placed in forward

direction along the normal to the target surface.

The comparison of the experimental parabolas (Fig.

3a) with the simulation spectra (Fig. 3c) allows us to

evaluate the particle masses, energy and charge states.

The spectra indicates a maximum proton energy of

1.5 MeV namely, higher value than those determined

by using polyethylene targets without nanotube

inserted.

The complexity of the laser interaction mechanisms

with solid targets is due to the non-linearity of the

processes occurring in the pre-plasma and of the

plasma non linear optical properties which are

dependent on the laser intensity and that occurs

generally above a threshold of about 1014

W/cm2 [8].

Self-focusing effects, for example, increases the

intensity of the part of laser beam on the target due to

the higher focusing which may reduce the spot up to

dimensions comparable with the laser wavelength.

Evidence of the self-focusing occurrence may be given

by IEA spectrometer of the emitted particles indicating

ion energy, masses and charge states.

The plot of the ion yield versus the focal position

indicates that for low charge states ions are due to

ionization by thermal electrons generated by inverse

bremsstrahlung mechanism. In contrast, ions with

higher charge states, connected with the presence of

fast electrons, and generated by resonant absorption

mechanisms, create a maximum yield, kinetic energy

Yie

ld

(V)


74

and charge sates when the laser focal position if placed

near and in front of the target surface.

Fig. 3: Typical experimental spectrum related to

Thomson Parabola placed in forward direction

with respect to the thin target with nanostructures

embedded in polyethylene (a), scheme of the TPS

spectrometer (b) and comparison with the

parabola simulation plot (c).

In the dense vapor generated in front of the target, in

facts, the ambipolar acceleration of ions due to non

linear forces, including ponderometive relativistic and

self-focusing, which lead to very high laser intensity in

a self-focused channel may become the main reason for

the presence of high kinetic energy and high charged

ions. Such a result was ascribed to the volume effect of

produced plasma due to the interaction of continuously

decreasing diameter of the laser beam with respect to

the target surface that, in the case of self-focusing

mechanisms, is found to a forward negative focus

position.

Fig. 4a shows a typical example of IEA spectrum

obtained by irradiating Au target in no condition of

self-focusing, when the focal position is FP = + 500

m, with the focal position inside the target and high

spot dimension.

In such conditions the self-focusing cannot happen

because the intensity is below the threshold value and

the number of charge states is only six. The inset of the

figure shows a streak camera X-ray image and a

scheme indicating with high precision the used focal

position. Fig. 4b shows a typical example of IEA

spectrum in conditions of self-focusing, when the focal

position is FP = -200 m.

In such conditions the number of charge states is

about 56 as result of hotter energetic plasma. Also in

this case the inset of the figure shows the streak camera

X-ray image and the scheme indicating the used focal

position. This last effect occurs because the high light

refraction effect produces a further laser beam

focalization, due to the dense plasma volume in front

of the target, which converges the beam so as a

focusing lens.

At higher intensities the data were collected from

literature and compared with our measurements in

order to evaluate the generalized law of I2 scale factor

[9].

Generally a linearity of processes occurs with the

law I2, however over linear dependences occur when

resonant absorption and self-focusing take place.

Discussion and conclusions

The existence of an optimum laser focus position for

generation of the fastest ions with the highest charge

states in front of the target surface is consistent with

literature [10]. The course of dependencies and similar

values of the highest Zmax indicate a threshold for the

appearance of relativistic self-focusing of laser beam

and a principal limitation of the maximum attainable

laser intensity. At PALS differences for 1 and 3

could be ascribed to a different absorption of laser

radiation, in accordance with the scaling relation I2.

The front part of the 300 ps laser pulse interacts with

the target and creates an expanding plasma plume.

Considering for simplicity, the expansion velocity v =

Detector

s

z

x

-V/2

+V/2

B E

N

S

gegmD1

L12

D2

L1

Ld1

Ld2L2

Pinholes

Detector

s

z

x

-V/2

+V/2

B E

N

S

gegmD1

L12

D2

L1

Ld1

Ld2L2

Pinholes

C5+

a) Thomson Parabola

Spectrometer

C2+

C3+

C4+

H+

Ep = 1.5 MeV

b)

c)

C 5+

a)

Thomson Parabola

Spectrometer C 2+

C 3+

C 4+

H+

c)

C 1 +

C6+


75

106 m/s, the plasma plume attains the distance of 100

m within the first 100 ps. For the laser beam diameter

of 70 m, the self-focusing length should be about 100

to 200 m, at least. For FP = 0, the more the plasma

plume expands, the longer the interaction length, but

the lower the laser intensity with which the front of the

plasma interacts.

Fig. 4 Typical IEA spectrum obtained at high

intensity laser at PALS laboratory in Prague

relative to Au target irradiated in no self-

focusing condition (a) and in self- focusing

condition (b).

The following conclusions can be made:

Nano and micrometric structures, such as carbon

nanotubes, polymeric chains and molecular groups

with dimensions comparable with the laser wavelength

may induce resonant absorption effects increasing the

plasma temperature and the acceleration ion drive

mechanisms;

Resonant effects seem to be influenced by structure

and composition of the target, by the plasma frequency

and occur at high intensity and in the contrary of the

literature also at low intensities, like we showed in this

work.

Self-focusing processes influence significantly the

generation of ions with the highest charge states, using

high power iodine laser with the pulse length of 300 ps

and an optimal FP distance can be found to enhance

this effect of intensity increase due to the focal spot

decreasing.

Acknowledgements

Work supported by LaserLabEurope (Project No.: pals

001653) and by INFN-LIANA Project.

References [1] H. Cai, W. Yu, S. Zhu, C. Zheng, L. Cao, B. Li, Z. Y. Chen and

A. Bogerts, Physics of Plasmas 13, 094504, 2006; [2] W. L. Kruer, Physics of Laser Plasma Interactions Addison-

Wesley, New York, 1988;

[3] S. C. Wilks and W. L. Kruer, IEEE J. Quantum Electron. 33, 1954, 1997;

[4] L. Torrisi, D. Margarone, L. Laska, J. Krasa, A. Velyhan, M.

Pfeifer, J. Ullschmied, L. Ryc Laser and Particle Beams 26, 379-387, 2008;

[5] E. Woryna, P. Parys, J. Wolowski, and W. Mroz, Laser Part.

Beams 14, 293, 1996; [6] L. Torrisi, G. Foti, L. Giuffrida, D. Puglisi, J. Wolowski, J.

Badziak, P. Parys, M. Rosinski, D. Margarone, J. Krasa, A.

Velyhan and J. Ullschmied J. Appl. Phys. 105, 123304, 2009; [7] L. Torrisi, S. Gammino,L. Andó, L. Laska, J. Krasa, K.

Rohlena, and J. Ullschmied, J. Wolowski, J. Badziak, and P.

Parys J. of Appl. Physics 99, 083301, 2006; [8] L. Laska, L. Ryc, J. Badziak, F.P. Boody, S. Gammino, K.

Jungwirth, J. Krasa, E. Krousky, A. Mezzasalma, P. Parys, M.

Pfeifer, K. Rohlena, L. Torrisi, J. Ullschmied and J. Wolowski Rad. Eff. & Def. in Solids 160 (10–12) (2005) 557–566;

[9] L. Laska, K. Jungwirth, J. Krasa, E. Krousky, M. Pfeifer, K.

Rohlena, J. Ullschmied, J. Badziak, P. Parys, J. Wolowski, S.

Gammino, L. Torrisi and F.P. Boody, Laser and Particle Beams

24(1), 175-179, 2006;

[10] L. Laska, K. Jungwirth, J. Krasa, M. Pfeifer, K. Rohlena, J. Ullschmied, J. Badziak, P. Parys, L. Ryc, J. Wolowski, S.

Gammino, L. Torrisi and F.P. Boody, Czech. J. of Physics 55

(6), 691-699, 2005.

NO SELF- FOCUSING

SELF- FOCUSING EFFECT

TOF ( s)

a)

b)


76


77

BARYON SPECTROSCOPY BY VECTOR MESON PHOTO-PRODUCTION

AT BGO-OD EXPERIMENT

V. De Leo a,b,*

, F. Curciarello a,b

, G.Mandaglio a,b

, M.Romanyuk a,b,c

, G.Giardina a,b

.

a)Dipartimento di Fisica, Università di Messina, I-98166, Messina, Italy

b)INFN- Sezione Catania, I-95123,Catania, Italy

c)Institute for Nuclear Research, National Academy of Science of Ukraine, Kiev, 03680, Ukraine


Abstract

The study of baryon resonances plays the same role

for understanding of the nucleon structure as the

nuclear spectroscopy was for the investigation on the

atomic nucleus structure. Excitation energies and

quantum numbers of the low lying nucleon resonances

are well known. Properties like mass, spin, and parity

alone , however, do not offer stringent tests of hadron

models. Much more crucial tests are provided by the

investigation of transitions between the states, which

reflect their internal structure. The dominant decay

channel of nucleon resonances is the hadronic decay

via meson emission. Photo-production of mesons,

which carries information on strong and

electromagnetic decay properties, therefore provides a

very valuable tool for their study. The progress made in

the last years in accelerator and detector technologies

has largely enhanced our possibilities to investigate the

nucleon with different probe. The new generation of

electron accelerators equipped with tagged photon

facilities have opened the way to meson photo-

production experiments of unprecedented sensitivity

and precision. The possibilities of the starting

international experiment BGO-OpenDipole (linked to

the I.N.F.N. MAMBO experiment) at the ELSA

facility of Bonn, which involves the hardware testing-

improvement and software production contributions of

the Messina group will be described in detail in the

present report. The experiment represents a new

sophisticate electromagnetic probe for the investigation

of baryon resonances by the meson decay detections.

Introduction

Current issues in the understanding of the strong

interaction address the structure of hadrons, consisting

of quarks and gluons, as the building blocks of matter.

Central challenges concern the questions why quarks

are confined within hadrons and how hadrons are

constructed from their constituents. One goal is to find

the connection between the parton degrees of freedom

and the low energy structure of hadrons leading to the

study of the hadron excitation spectrum but the

excitation spectrum of the system does not provide

very sensitive tests of models [1]. The crucial tests

come from the investigation of transitions between the

states which are more sensitive to the model wave-

function. The dominant decay channel of nucleon

resonances is the hadronic decay via meson emission

to the nucleon ground state [2]. However, photon decay

amplitudes are also of great interest since the photon

couples only the spin flavor degrees of freedom of

quarks and therefore reveals their spin-flavor

correlation which are related to the configuration

mixing predicted by the QCD [3]. Perturbative QCD at

high energies deals with the interactions of the quarks

and gluons. However, our picture of the nucleon has

much more to do with effective constituent quarks and

mesons that somehow subsume the complicated low

energy aspects of the interaction which generate the

nucleon many body structure of valence quarks, sea

quarks and gluons. The most important step towards an

understanding of nucleon structure is therefore the

identification of the relevant low-energy effective

degrees of freedom. Most nucleon models are based on

three equivalent constituent quarks interacting via

some QCD ―inspired‖ interaction. However, models

based on quark-diquark (q – q2) configurations were

also suggested and more molecular-like pentaquark

( qqq qq ) structures have been discussed in the

context with certain ―nucleon‖ resonances. From the

experimental point of view the main difference

between nuclear and nucleon structure studies results

from the large, overlapping widths of the nucleon

resonances and much more important non resonant

background contributions which both complicate

detailed investigations of the individual resonances.

The existing data for nucleon resonances were

mostly determined by πN scattering. The comparison

of the set of resonances predicted by modern quark

models with the set of experimentally established

resonances resulted in the so-called ‘missing

resonances‘ problem [4]: more resonances are

predicted than observed. This problem encouraged the

use of the photo-production of mesons as an alternative

tool to excite the resonances. The advent of a new

generation of electron accelerators allowed to perform

meson photo-production experiments of unprecedented

sensitivity and precision [5].

Pion scattering on a proton target has been chosen as

the best tool to excite and to study the resonances of

the nucleon. Nucleonic resonances are excited states of

the nucleon with large mass width but with well

defined spin, isospin and parity. Their identification


78

and their characterization were carried out through the

analysis of the pion-nucleon scattering data by partial-

wave phase-shifts method. In this method, the

excitation of a given resonance is searched with the

amplitude behaviour of a specific partial wave in a

characteristic plot called Argand diagram [6].

The Jπ

of the pseudo-scalar mesons (pions, eta,

kaons) is 0−. The J

π of the vector mesons (rho, omega)

is 1−. The isospin of pions, kaons and η is 1, 1/2 and 0

respectively. The isospin is 1 for ρ and 0 for ω. All of

the mesons have a short lifetime (≤ 10−7

s); however, π±

and K± may have a path of several meters in the

laboratory and then be detected with standard detectors

similarly to stable charged particles, whereas η, η' , ρ

and ω decay almost at their production point. It is

worth mentioning that the rare decay modes are used as

special tools to test chiral perturbation theory and basic

invariance principles.

Experimental set-up.

A schematic view of the experimental apparatus used

in the S-beamline of Bonn is shown in Figure 1. The

Electron Stretcher Accelerator consists of three stages

(injector LINAC, booster synchrotron and the stretcher

ring) and provides a beam of polarized and unpolarized

electrons with a tunable energy of up to 3.5 energy

GeV. The bunched electron beam impinges on a

radiator. Scattered electrons produce bremmstrhalungg

with the tipical 1/Eγ spsectral distribution.

The polar angular region of small angles (θ < 12°) is

covered by B1-magnetic field spectrometer that

produces a dipolar field of about 0.5 T and that will be

used for the separation, identification and

reconstruction pulse resolution (0.5%) of charged

particles emitted in the photo-production process.

Figure 1. Schematic view of S - beamline

accelerator ELSA in Bonn.

For this purpose, the spectrometer is equipped with:

- MOMO is a scintillating fiber vertex detector with

672 channels. It consists of three layers of 224 parallel

fibers (2.5mm diameter) each. The layers are rotated by

60° against each other. The arrangement yields a

circularly shaped sensitive detector area of 44cm

diameter. The spatial resolution is about 1.5mm,

yielding effectively more than 50 000pixels. A 5cm

wide central hole allows the photon beam to pass

through [7].

Figure 2. MOMO detector.

- The aerogel Čerenkov detector (ACD) that serves

to reliably discriminate pions against protons, and

particularly improves the K± identification

substantially.

- SciFi2 detector where an active area of 66cm x

51cm is obtained using 640 scintillating fibers with a

diameter of 3mm [7].

Figure 3. SciFi2 detector.

A central hole (4cm x 4cm) allows the beam to pass

through. Groups of 16 fibers are glued together to form

a so-called module. The design guarantees a minimum

path length (about 2mm) for particles traversing the

circular fibers. The modules are arranged in two layers

twisted by 90 degrees.

- Tracking of charged particles behind the

spectrometer magnet is performed with eight horizontal

drift chambers (DCs) which are built at the PNPI

Gatchina. To cover the necessary angular range each

DC has a sensitive area of at least 2456mm × 1232mm.

The photon beam has to penetrate the DCs. The

distance of the chambers from the target will range

from 3.7 m for the first chamber up to 4.7 m for the

last. For accurate positioning and simplified handling

the chambers will be hanging from two support beams


79

attached to the magnet. Four of the chambers will be

rotated by ± 9 degree around the beam axis. With two

of the remaining chambers having horizontal wires and

the other ones vertical wires four different wire

orientations are obtained.

- The forward spectrometer will be complemented by

a time-of-flight (TOF) detector, which is an essential

component for particle identification, because it

provides flight-time measurements for both, charged

particles and neutrons. It has to cover the inner 10-12

degree angular range at a distance of 5m downstream

of the target. It consists of four walls with a 3×3 m2

front surface, mounted on independent mechanical

stands. Each wall houses 14 individual scintillating

bars of 3000 mm × 200 mm × 50 mm size with

photomultiplier readout at both ends.

The polar angular region between 25 and 155

degrees is covered by:

- The BGO (Bi4 Ge3 O12) Rugby Ball is a large

acceptance calorimeter designed to measure multi-

photon states with excellent energy resolution. The

design of the calorimeter has taken into consideration a

constant thickness in every direction and a central hole

of radius 100 mm for the passage of the beam, target

and inner detector housing. The resulting structure is

made of 480 truncated pyramidal crystals of 240 mm

length (corresponding to ~ 21 radiation lengths)

arranged in a 15×32 matrix covering the polar angles

from 25° to 155° and the whole azimuth for a total

solid angle ΔΩ = 11.3 sr. The mechanical structure

consists of 24 carbon fibers baskets, each containing 20

crystals, and supported by an external steel frame.

Figure 4. Overhead view of the BGO

calorimeter.

The baskets are divided into cells to keep the crystals

mechanically and optically separated. The thickness of

the carbon is 0.38mm for the inner walls and 0.54 mm

for outer walls. The steel support frame is separable

into two moving halves to allow to access the central

part of the detector [7].

- A cylinder of 32 plastic scintillator bars, which

allows, trough the ΔE measure, the discrimination

between charged and neutral particles and in

combination with the energy released in the

calorimeter, the identification of charged particles

(protons and pions).

- The target can be a proton or deuterium target.

Hardware testing

To install the BGO system in Bonn it was necessary

to replace most of electronic acquisition and HV

distribution system to the crystal.

The reading of the BGO signal amplitude is made by

sampling ADC modules 32 -channel multiplexer. The

main characteristics of the ADC modules (AVM16

MAMBO) are the following:

-Sampling frequency 160 MHz (= 6.25ns)

-12 bit resolution (corresponding to 4096 channels)

-16 signal input and one trigger input.

The sampling of the signal occurs within a time

interval defined by the user that can begin even before

the trigger signal (in our case the time window width is

800ns). The initial samples (four) are dedicated to the

determination of the baseline event subtracting

automatically the value determined at the signal; the

outgoing signal is thus cleaned of any background. The

tests on the ADC modules were performed working

with external signals and triggers, coming from a pulse

generator by setting 9 different possible offset values

on the baseline value. For each baseline, we have been

sending a pulser signal with an amplitude varying from

100 mV to 10 mV with steps of 10 mV. The signal

coming from the pulser is a wave with trapezoidal

shape, time width 200 ns, rise time 5 ns, frequency 1

kHz. The procedure followed for the tests with the

pulser and different baselines is the following: at first

no signal is sent to the ADC and the baseline offset is

set; then the baseline register is read and only at this

time the signal is sent to the ADC. The value of 100

mV on the pulser current is fixed and then the baseline

register is read again and the acquisition program is

started; thus the acquisition program is stopped and the

value of 90 mV on the pulser current is fixed. As

before, the baseline register is read again and the

acquisition program is started; this procedure is made

for ten values of current (form 100 mV to 10 mV). The

test results have highlighted some problems of the

ADC modules. Strong difference was shown in the

extracted value of the total integral (Qtot) with a same

input signal between different modules and different

channels. The response of the ADC channels to a fixed

input strongly depends on the baseline offset (the

response strongly increases with baseline value

reaching a ―plateau‖ only for the higher baseline

values). The linear behavior was checked and it was

confirmed for almost all baseline offset values but the

strongly dependence of the gain on the baseline offsets

affects the ADC linearity. Therefore, the time

synchronization features between ADC modules have

been verified. The tests on ADC modules have enabled

their improvement.


80

Physics

The goal of this project is the systematic

investigation of the photoproduction of mesons off the

nucleon. Polarization measurements are indispensable

to characterize the relevant degrees of freedom in the

production process of the different mesons, in

particular the formation and role of hadronic

resonances. The photoproduction of mesons off the

nucleon provides access to several aspects of low-

energy strong interaction.

The quark model predicts a large number of nucleon

resonances which have not yet been observed [8].

Since the most used reaction for their study was pion-

nucleon scattering, one could infer that these so-called

‗‗missing resonances‘‘ may couple weakly to this

channel[9]. One possibility to investigate this issue is

the photo-production of ω mesons off the proton. This

channel is interesting for several reasons: first, there is

no nucleon resonance well-established decaying by ω

emission; second, the threshold of ω-photoproduction

lies in the third resonance region, which is less

explored than the first two; third, from the sparse data

in the literature and a new generation experiment,

evidence for resonance excitations in

γ p→ ωp is still not obvious.

Due to the fact that the ω is isoscalar (I=0), the s-

channel production of this meson is only associated

with the decay of N∗ (I=1/2) states and not the decay of

Δ∗ (I=3/2) states, which greatly simplifies the

contributing excitation spectrum. However the vector

meson character of the ω implies that at least 23

observables have to be measured to disentangle all

contributing resonances, instead of 8 in the

pseudoscalar case. It can be hoped however, that fewer

than 23 observables already provide significant

constraints. In any case, the measurement of

polarization observables will provide important

information about the ―production mechanism‖ of the

ω meson[10]. At high photon energies resonances play

no role.

The cross section of vector-meson production off

nucleons falls off exponentially with the squared recoil

momentum, t, corresponding to the range of the mutual

interaction. The t dependence of the cross section,

which is approximately the same for all sufficiently

high photon energies, is characteristic for

‗‗diffractive‘‘ production. It is associated with the

exchange of natural parity quantum numbers (Fig. 1

left) related to the Pomeron, a composite gluonic or

hadronic structure.

At large |t| deviations from pure diffraction show up.

From the comparison to QCD-inspired models which

are also able to describe φ and ρ0 photoproduction, the

presence of hard processes in the exchange itself was

thus also included at |t|>1 GeV2.

Figure 5.Contributions to ω-photoproduction: natural

parity t-channel exchange (left), unnatural parity π0 t-

channel exchange (middle), s-channel intermediate

resonance excitation (right).

Because of the sizeable ω→ π0γ decay (8%),

significant unnatural parity π0

exchange has been

expected for ω-photoproduction at smaller energies

(Fig.1 middle). It was indeed observed and found

dominating close to threshold. However, neither

Poimeron nor π0

exchange are able to reproduce the

strong threshold energy dependence of the cross

section and the ω decay angular distribution observed

in exclusive photoproduction and electroproducton.

This was interpreted as possible evidence for s-channel

contributions (Fig.1 right)[11].

Experimental support comes from a first

measurement of photon-beam asymmetry, Σ , through

the GRAAL collaboration[6,12].

The threshold ω-photoprodution is Eγ = 1.1 GeV; ω

meson decays mainly into channels:

0

0

( . . 89%)

( . . 8.9%)

B R

B R (1)

In Bonn, the load decay channel can be observed very

well by combining the BGO (π0) and the spectrometer

(π + π

-).

Moreover, the spectrometer allows a more detailed

study of other vector-meson such as the ρ-meson. Its

main decay modes (to almost 100%) proceed via ρ0 →

π+ π

-, ρ

+ → π

+ π

0 and ρ

- → π

- π

0 . In particular, the last

two decays that derive from the ―twins‖ reactions γ p

→ ρ+

n and γ n → ρ- p may be confused in case of the

proton inefficiency combined with neutral noise, for

this reason the BGO - spectrometer combination is

crucial.

REFERENCES

[1] F. Wilczek, hep-ph/0201222v2;

[2] G. Mandaglio et al., Phys.RevC 82, 045209(2010); [3] R. Di Salvo et al., Eur.Phy. J A 42,151 (2009);

[4] A. Fantini et al., Phys.RevC 78, 015203 (2008);

[5] B. Krusche, Czech. J. Phys. 49 (1999); [6] E. Hourany, Romanian Reports in Physics, Vol. 59, No. 2, P.

457–472, 2007;

[7] http://b1.physik.uni-bonn.de/ExperimentalSetup; [8] S. Capstick and W. Roberts, Prog. Part. Nucl. Phys. 45, S241

(2000);

[9] J. Ajaka et al., PhysRevLett. 96, 132003 (2006); [10] A. V. Sarantsev, A. V. Anisovich, V. A. Nikonov and H.

Schmieden, Eur. Phys. J. A 39 , 61–70 (2009); [11] F. Klein, PhysRevD.78, 117101 (2008);

[12] V. Vegna et al., in preparation.

http://b1.physik.uni-bonn.de/ExperimentalSteup


81

DIODE LASERS FOR OPTICAL TRAPPING APPLICATIONS

R. Sayeda,b,

*, G. Volpec, M. G. Donato

b, P. G. Gucciardi

b, and O. M. Maragò

b

a)Dottorato in Fisica dell’Università di Messina, Dip.to di Fisica, F. S. D’Alcontres 31, 98166 S. Agata-Messina, Italy

b)CNR-IPCF, Istituto per i Processi Chimico-Fisici, V.le F. S. D’Alcontres, 37, I-98158, Messina, Italy

c)Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, 70569 Stuttgart, Germany


Abstract

Diode lasers can be built to meet stringent

specifications on beam stability, optical beam shape,

wavelength stability, thermal stability, and compact

dimensions. Stabilization of laser frequency is essential

for various research fields such as metrology, frequency

standards, and optical communications. Here we discuss

how diode lasers can be employed in optical trapping

applications, where a laser beam is tightly focused with a

high numerical aperture objective at the diffraction limit

to trap particles near its focal spot. In this context we will

describe a novel approach to optical trapping based on

optical feedback that can be applied with low numerical

aperture lenses.

Keywords: Diode lasers, optical feedback, frequency

stabilization, optical trapping.

Introduction

Since their first use in atomic physics in the early 80's,

diode lasers have become an important part of many

modern experiments [1]. This is primarily driven by the

fact that they are compact, cost effective, small sized, and

highly efficient [2]. For the application of diode lasers in

high resolution laser spectroscopy, linewidth reduction

and frequency stabilization have been actively

investigated to improve the poor spectral quality of diode

lasers.

In principle these systems are able to achieve high

stability in their output intensity and frequency (up to

10-11

). However frequency and intensity stability are

considerably dependent on operational supply current and

on laser diode chip temperature. Thus it is crucial to

minimize fluctuations of these operational parameters. A

laser diode is very sensitive to static electricity and EM

interference. Its quality shielding and galvanic separation

of signal wires from supply wires is not useless

complication.

Our interest in diode lasers lies in their applications for

novel approaches to optical trapping and laser cooling of

nano and microparticles. The ability to exploit light forces

for the trapping and handling of microparticles was

pioneered by Ashkin [3] in the 1970‘s. Some years later

the first optical tweezers (OT) was realized [4] using a

laser beam strongly focused by a high numerical aperture

objective lens. In these systems a particle is trapped in the

focal region of the lens by the forces arising from the

scattering of light by the particle [5,6] (see Fig. 1).

Fig. 1: (left) Ray optics interpretation of optical forces on

a dielectric sphere. (a) A light-ray (red) exerts a force

(dark gray) arising from its refraction and reflection. (b)

The forces on the sphere (dark gray) due to two light-rays

(red and orange) compensate each-other at the

equilibrium position. (c) Restoring force on an axially

displaced sphere. (d) Restoring force on a laterally

displaced sphere. (right) Exemplar 2 m latex spherical

particle optically trapped in our laboratory with a diode

laser at 830nm.

Since then, OT have been extensively used for

applications in cellular and molecular biology, soft matter

and nanotechnology. In biology, OT are used to make

micro-mechanical experiments on cells and

microorganisms both in vitro and in vivo [7-9], where the

use of a near infrared wavelength (800nm-1100nm) laser

prevents photodamage and thus the death of

microorganisms and cells [9]. In physics, the ability to

apply forces in the range of pico-Newton to micro- and

nanoparticles and to measure their displacements with

nanometer precision is crucial for investigation of

colloidal and condensed matter systems [10]. More

recently OT have been also used to manipulate, rotate and

assemble a variety of nanostructures, such as carbon

nanotubes [11-13], nanowires [14,15], polymer

nanofibers [16], graphene flakes dispersed in water [17]

and metal nanoparticles [18] and aggregates [19,20]. Here


82

we discuss a novel application of diode laser to optical

trapping based on optical feedback-locking.

Theory and Overview

Optical Feedback. The sensitivity of the output

intensity of a diode laser to both the amplitude and phase

of external feedback is well documented [21]. The effects

of optical feedback on the behavior of diode laser have

shown that the dynamical properties of injection lasers are

significantly affected by the external feedback, depending

on the interference conditions between the laser field and

the delayed field (returning from the external cavity). The

essence of the optical feedback method is to increase the

quality factor of the laser resonator, therefore narrowing

the linewidth and stabilizing the laser's wavelength [22].

It is well known that external optical feedback strongly

affects the properties of semiconductor lasers, the

returned light into laser cavity causes variation in the

lasing threshold, output power, linewidth, and laser

spectrum. Under lasing conditions, the diode cavity is

filled with gain medium, which, to a large extent,

compensate for the diode cavity loss. It, therefore, has

substantially greater effective quality factor, and

consequently, greater influence on the laser behaviors,

than the passive external cavity. For this reason, the

following form of field equation has been adopted for a

compound cavity laser configuration, obtained by adding

an external feedback term to a standard laser equation in

complex form [21], that is:

)t(iti

0N

ti

e)t(kEe)t(E

)n(G2

1)n(ie)t(E

dt

d

(1)

Here, N n is the diode cavity longitudinal mode

resonant frequency and 0 is the cavity loss of the diode

cavity, is the laser oscillation frequency, E t is the

field amplitude, and is the transit time in the external

cavity. The last term on the right hand side represents the

external feedback and the coefficient k is related to cavity

parameters as,

/ 2 Dk c l (2)

Where c is the speed of light, Dl is the cavity length of

diode laser, and is refractive index of the active region.

The parameter defined with the facet and external

mirror reflectivities 2R and 3R as

2/1

232 )R/R)(R1( (3)

It is a measure of the coupling strength between the two

cavities. In the above expression for external feedback,

multiple reflections in the external cavity have been

neglected.

Optical Trapping. In an OT the trapping force arises

from the presence of a gradient in the intensity of the

optical field and tends to attract particles with refractive

index higher than their surrounding towards the high-

intensity regions of the field (high-field seekers), and

conversely particles with lower refractive index towards

the low-intensity regions (low-field seekers) [3-6]. Using

simple ray diagrams it is possible to provide a very

detailed picture of the physics of the trapping process,

without the need for the use of involved calculus and

electromagnetic theory. As can be appreciated from Fig.

1(a), when a light ray enters a transparent dielectric

sphere it undergoes deflection as a result of refraction at

the interfaces. Such deflection of photons that carry

momentum results in a recoil force. This force (dark gray

arrow in Fig. 1(a)) however does not trap the particle; it

only pushes the sphere away from the light. To trap an

object it is necessary to use a set of light-rays coming

from different directions. If two light-rays come from

opposite sides of the dielectric sphere at a very high angle

they can indeed trap the particle (Fig. 1(b)). It can be

easily appreciated from similar ray diagrams what

happens when the sphere is displaced both axially (Fig.

1(c)) and laterally (Fig. 4(d)) with respect to the focus. In

this cases the total force (black arrow) pushes the particle

towards the optical trap center arises.

A simple example is a highly focused laser beam. This

acts as an attractive potential well for a particle. The

equilibrium position lies near – but not exactly at – the

focus. When the object is displaced form this equilibrium

position, it experiences an attractive force towards it. This

restoring force is in first approximation proportional to

the displacement; in other words, the force in the OT is

well described by Hooke‘s law:

Fx= - Kx (x - x0) (4)

where x is the particle‘s position, x0 is the focus position,

and kx is the optical trap spring constant along x, usually

referred as trap stiffness. In fact, optical tweezers create a

3D potential well that can be approximated by three

independent harmonic oscillators, one for each of the x, y,

and z directions. In the xy-plane (perpendicular to the

direction of the beam propagation) the force is mainly due

to gradient optical forces, while along the z-direction

(along the direction of the beam propagation) the

restoring gradient force is weakened by the presence of

radiation pressure that pushes the particle away from the

focal spot.

More complex intensity patterns have been obtained, for

example, by interfering two or more light beams or by the

use of advanced techniques such as holography and time-

multiplexing.


83

Experimental Setup

In our experiments, standard optical trapping is

generally achieved by focusing a 830 nm laser beam

(from a laser diode Sanyo DL8142-201, 150mW nominal

power) through a 100× oil immersion objective (NA=1.3)

in an inverted microscope configuration (see Fig. 2 for a

sketch). The laser power available at the sample is about

20mW and is kept constant during the optical force

measurements. Optically trapped particles (generally latex

beads with 2 m diameter) are imaged with a CCD

camera (see Fig. 1).

Fig. 2: Sketch of the experimental setup and methodology

for feedback-controlled optical trapping. (left) When no

particle is trapped the optical feedback on the diode laser

is on and the available power at the sample permits to

efficiently attract particles at the focal spot of the low

numerical aperture objective. (right) When a particle is

trapped the feedback is off and the trap works at lower

power.

For the realization of feedback controlled optical

trapping we employ a low numerical aperture objective

(NA=0.5). In fact, feedback controlled trapping may

release the stringent requirements on numerical aperture

for the operation of standard OT. In brief, in this novel

configuration (see Fig. 2) the optical feedback on the

diode laser source is controlled by the light scattering

from a trapped particle.

When no particle is in the trap, the optical feedback

from a dielectric mirror posed above the microscope

objective will increase the trapping power in the focal

spot. Instead, when a particle falls in the trap the optical

feedback will stop and trap will work at low power

preventing damage and relaxing the stringent conditions

on high numerical aperture for standard OT.

Results and Discussion

The resulting optical force in feedback-controlled

optical trapping is regulated by the response of the light

source to the optical feedback, so it is useful to study the

characteristics of diode lasers. Three diode lasers at

different wavelengths and different output power have

been studied.

0 20 40 60 80 100 120

0

20

40

60

80

Po

we

r (m

W)

Injected current (mA)

T= 18 OC

Ith

= 33 mA

I

P

Fig. 3: L.I. curve for diode laser (Sanyo

DL7140201S, 785nm, 80 mW). The measured

threshold current is Ith=33 mA.

The most important parameter of diode lasers to be

measured is the degree to which it emits light as current is

injected into the device. This generates the output light

versus input current known as the L.I. curve. As shown in

Fig. 3 the L.I. curve for diode laser (Sanyo DL7140-201S,

785 nm, 80 mW), as the injected current is increased the

laser first demonstrates spontaneous emission which

increases very gradually until it begins to emit stimulated

radiation, which is the onset of laser action. The exact

current value at which this phenomenon takes place is

typically referred to as the threshold current, Ith. It is

generally desirable that the threshold current be as low as

possible. It is one measure used to quantify the

performance of a diode laser.

The second parameter we measured is differential

external quantum efficiency of the diode laser ηD. This is

defined as the ratio between the number of photons

exiting the laser (∆P/hυ) to the number of electrons

injected per unit time into the laser (∆I/e) and it has a

typical value ranging between 0.2 and 0.7 for continuous

wave lasers.

/

/D

P hv e P

t e hv t (5)

where e is the electronic charge, υ is the frequency of the

radiation, h is the Planck constant and ∆P/∆I is the slope

efficiency of diode laser.

By measuring the output power light versus current (L.I.)

curve of the diode lasers Toptica photonics DL100 (403


84

30 40 50 60 70

0

5

10

15

20

25

30

Ou

tpu

t p

ow

er

(mW

)

Injected Current (mA)

T1= 20

oC

T2= 29

oC

Linear Fit of T= 20 oC

TO= 85.5 K

nm, 30 mW), diode laser Nichia NDHV310ACAE1 (417

nm, 30 mW) and diode laser Sanyo DL 7140-201S (785

nm, 80 mW), the ηD is 0.28, 0.22 and 0.65 respectively. The third parameter that has been measured is the internal

quantum efficiency of the diode laser ηI. It is defined as

the fraction of the injected carriers that recombine

radiatively and it is given by;

I

P

v t (6)

where V is the power supply voltage. ηI for diode laser

Toptica Photonics DL100 is 19 % , for diode laser Nichia

NDHV310ACAE1, 417 nm, 30 mW, is 15 % and for diode

laser Sanyo DL7140- 201S is 26 % which is calculated

from slope efficiency of the experimental L. I. curve for

each laser.

Finally the characteristic temperature of the diode laser,

To, is calculated which is defined as a measure of the

temperature sensitivity of the device and dependent on the

particular diode whose value is a measure of the quality

of the diode. Higher values of To imply that the threshold

current and external differential quantum efficiency of the

device increase less rapidly with increasing temperatures.

This means the laser being more thermally stable. Usually

To ranges from 70 K for the worst diodes to 135 K for the

best ones [23].

The ratio between the threshold values at two

temperatures differing by ∆T is given by (Ith1/Ith2) = exp

(∆T/To). The experimental work to determine the

temperature characteristic of the GaN diode laser Toptica

Photonic DL100 was made by measuring the light versus

current (L.I.) curve of the lasers at various temperatures

as shown in Fig. 4.

Fig. 4: L.I. curve at two different temperatures for

diode laser Toptica, 403 nm, 30 mW.

From the experimental work the T0 for diode laser Toptica

DL100 (403 nm) is equal to 85.5 K, T0 for diode laser

Sanyo DL 7140 201S (785 nm) is equal to 86 K and T0

for diode laser Nichia NDHV310ACAE1 (417 nm), is

equal to 137 K. These results for all diode lasers showed

good agreement with theoretical values. The diode laser

Nichia NDHV310ACAE1 (417 nm) resulted to be the

best diode laser being less sensitive to temperature

changes.

Summary

To summarize, diode lasers are perfectly suited for

optical trapping applications thanks to their low cost, user

friendly operation, long term stability in output power and

frequency. Both micro and nanoparticles (nanotubes,

nanowires, graphene) are routinely trapped and

manipulated in our optical tweezers experiments.

The sensitivity of diode lasers to optical feedback is the

crucial enabling property for feedback-controlled optical

trapping. The external optical feedback, when it is

sufficiently strong, results in a large stability of the diode

laser and it is much more easily detected than in other

lasers because of the strong dependence of the refractive

index of the diode laser active region on the carrier

density. Such novel approach will open perspective for

extending the use of light forces with low numerical

aperture lenses much increasing the trapping depth,

trapping efficiency and spatial range in experiments.

References [1] C. J. Foot, Atomic Physics, Oxford University Press, Oxford,

(2005);

[2] L. Ricci, M. Weidemuller, Opt. Comm. 117(1995)541; [3] A. Ashkin, Phys. Rev. Lett. 24 (1970) 156;

[4] A. Ashkin, et al. Opt. Lett. 11 (1986) 288;

[5] A. Jonas, P. Zemanek, 29 (2008) 4813; [6] F. Borghese, et al. Opt. Express 15 (2007) 11984;

[7] A. Ashkin, J. M. Dziedzic, T. Yamane, Nature 330 (1987) 769;

[8] M. D. Wang, et al. Science 282 (1998) 902; [9] Y. Liu, et al. Biophys. J. 68 (1995) 2137;

[10] D. Preece, et al. J. Opt. 13 (2011) 044022;

[11] O. M. Maragò, et al. Nano Lett. 8 (2008) 3211; [12] O. M. Maragò, et al. Physica E 8 (2008) 2347;

[13] P. H. Jones, et al. ACS Nano 3 (2009) 3077;

[14] P. J. Pauzauskie, et al. Nat. Mater. 5 (2006) 97; [15] A. Irrera, et al. Nano Lett. (2011), DOI: 10.1021/nl202733j;

[16] A. A. R. Neves, et al., Opt. Express 18 (2010) 822;

[17] O. M. Maragò, et al., ACS Nano 4 (2010) 7515;

[18] R. Saija R., et al. Opt. Express 17 (2009) 10231;

[19] E. Messina, et al. ACS Nano 5 (2011) 905;

[20] E. Messina, et al. J. Phys. Chem C115(2011) 5115; [21] C. Ye, Tunable External Cavity Diode Laser, (2004);

[22] B. Tromborg, J. H. Osmundsen, IEEE J. Quantum Electr., QE-20

(1984) 1023; [23] O. Svelto, Principles of Lasers, (1993).


85

INTERFERENCE WITH COUPLED MICROCAVITIES

R. Stassia, O. Di Stefano

a, S. Savasta

a

a) Dipartimento di Fisica della Materia e Ingegneria Elettronica,Università di Messina Viale S. D’Alcontres, 98166

S.Agata-Messina, Italy

Abstract

Here we propose an all-optical analogue of the effect of

sign change under 2π rotation based on time-resolved

optical interference in coupled optical microcavities.

Feeding the coupled-microcavity system with a pair of

phase-locked probe pulses, separated by precise delay

times, provides direct information on the sign change of

the transmitted field.

Introduction

In quantum mechanics if we want to perform a rotation

of a generic quantum state, we have to apply the operator

U(θ) = exp(-iJ·θ/2) on the corresponding ket. A rotation

by 2π radiants around the z-axis, which intuitively ought

to be equivalent to no rotation at all, multiplies the

eigenstate of J2 and Jz by −1 if j=n/2, with n integer, and

where J is the angular momentum operator. It is necessary

a rotation by 4π radians to return to its initial state. As

observables in quantum theory are quadratic in a wave

function, the change of sign cannot be detected by

ordinary experiments.

The first Gedanken experiments aimed at the

observation of the sign change of spinors under 2π

rotations were published by Bernstein and independently

by Aharonov and Susskind. These two proposed

experiments, the first involving the interaction of a spin

1/2 particle with a magnetic field, and the second

involving the tunneling of a current of free electrons,

were conceptually similar. In both cases one system was

split into two separate subsystems, one of them was

affected by an additional 2π rotation relative to the other

one, and then recombined. The first experimental

verification of coherent spinor rotation was provided by

Rauch et al. and Werner et al., both groups employed

unpolarized neutron interferometry as suggested in the

Bernstein-Gedanken experiment. Klein and Opat reported

the observation of 2π rotations by neutron Fresnel

diffraction.

The similarity of the mathematical description (that is, the

algebraic isomorphism) between spinor rotations and the

transitions between two atomic or molecular states of any

total angular momentum has been exploited to study

analogies of 2π spin rotations with different experimental

approaches that required no fermions. One other system,

where such an effect has been observed, consists of

strongly interacting Rydberg atoms and microwave

photons: after a full cycle of Rabi oscillation, the atom-

cavity system experiences a global quantum phase shift π.

We consider a system of two coupled planar

microcavities (MCs). When one of the two is excited by

an ultrafast resonant optical pulse, the energy oscillates

between the two systems until losses through the external

mirrors prevail. In such systems the coupling of the two

cavity modes can be controlled by the transmission of the

central mirror and the two resonant modes are the optical

analogs of two atomic or molecular states, which, in turn,

are isomorphic to a spin 1/2 system. We provide with this

system a concrete and conceptually simple all-optical

realization of the sign change under 2π rotations.

Two Coupled Oscillators with source term

A semiconductor planar MC is a structure formed by

high reflecting dielectric mirrors [distributed Bragg

reflectors (DBR)] on the two sides of a spacer (Sp) layer,

of physical length LC.

Here, we consider a system composed by two planar

MCs connected through a common DBR (see Fig. 1). We

assume that the two MCs have a high Q factor and that

the intracavity modes are coupled with the external field

via two partially transmitting mirrors. In the figure 2, the

dashed line represents the single mode of an empty

microcavity. The continuous line represents the splitting

in energy of the former mode when we couple two

identical microcavities. The two resonant modes are the

optical analogues of two atomic or molecular states,

which, in turn, are isomorphic to a spin 1/2 system. We

consider systems with coupling-induced splitting quite

larger than the linewidth of the individual peaks.

Figure 1: Scheme of a double microcavity


86

Figure 2: Resonant modes of (dashed line) one

empty MC and (continuous line) two coupled

MCs.

We consider excitation of the system by a Gaussian

light pulse arriving from the left of the coupled system

2

20

00 2

)tt(

)tt(

1 ee2

1)t( (1)

The calculated field intensity is shown Fig. 3. The

figure also displays (arb. units) the corresponding

Gaussian input pulse. The transmitted intensity displays a

damped oscillatory time behavior (with Rabi frequency

ΩR) originating from the combination of coherent energy

exchange between the two MCs and losses through the

external mirrors. To inspect the phase of the transmitted

field after one or two Rabi-like oscillations, we now

consider a second pulse in phase with the first one sent

from the left into the double semiconductor planar MCs.

The total input field can be expressed as,

2

21

10 2

)tt(

)tt(

12 ee2

1)t()t( (2)

The transmitted intensity is calculated for two different

physical situations as shown in Fig. 4 and 5. First we

address the case when the arrival time of the second pulse

is chosen so that the corresponding first maximum in the

transmitted field is exactly in time with the second

maximum originating from the first pulse Fig. 4. In

particular the time delay between the two pulses

corresponds to a complete Rabi-like oscillation: ΩR(t1-

t0)=2π. In this case we find that the total signal is strongly

damped due to destructive interference.

Figure 3: light field transmitted intensity inside the

cavity in function of time when is sent a single

excitation.

Figure 4: transmitted intensity calculated when a

second pulse is sent after one complete Rabi-like

oscillation.

Figure 5: transmitted intensity calculated when a

second pulse is sent after two complete Rabi-like

oscillations.


87

Hence, such an abrupt damping of the signal

demonstrates that the transmitted field after a complete

oscillation acquires a π phase (minus sign). If the arrival

time of the second pulse is chosen so that ΩR(t1-t0)=4π

(see Fig. 5) the total signal gets amplified due to

constructive interference. This condition is verified when

the corresponding first maximum in the transmitted field

is exactly in time with the next (third) maximum

originating from the first pulse.

Analytical Model

The essential physical features of such a system may be

understood through a simplified analytical model. We

adopt the quasimode approach. The discrete cavity modes

(one for each MC) interact with an external multimode

field. The quasimode approximation allows us to describe

such systems analogously to a two interacting oscillators

system. In particular, we consider a system of two

coupled harmonic oscillators (the light modes of the two

coupled cavities) with an external source ε(t). The

Hamiltonian of such a system can be written as

† † † †

0 0

† *

( )

( ) ( )

H a a b b g a b b a

t a t a (3)

where a and b are, respectively, the bosonic operators

relative to the single mode in each cavity, the coupling g

depends on the reflectivity of the central mirror, and ε(t)

describes the feeding of the cavity by a classical input

beam. The resulting evolution equations for the photon

operators inside the two cavities are

0

0

( )2

2

d ii a a g b a t

dt

d ii b b g a b

dt

(4)

where <・> indicates the mean value of the operator,

and γ takes into account the damping and losses of a field

inside the structure and may be considered as a

phenomenological parameter or as obtained from the

master equation for two coupled oscillators interacting

with a zero-temperature thermal reservoir. In the rotating

frame (putting ω0 = 0), if losses are neglected (γ = 0) and

considering the input field in the cavity as a sharp pulse

sent at t = t0 we obtain

0

0

0† 2

2

0† 2

2

( )cos

2

( )sin

2

1 cos ( )

2

1 cos ( )

2

R

R

R

R

t tAa i

t tAb

t ta a A

t tb b A

(5)

where ΩR = 2g/ħ represents the Rabi frequency. We

now calculate the number of photons emerging from the

cavity on the right, <b†b>, that can be measured by a

photodetector. Inspecting the last two equations, we

observe that it oscillates with a Rabi of frequency ΩR.

Instead, we observe, as is evident from the first two

equations, that b oscillates with a double period with

respect to the light cavity population (i.e., at a frequency

equal to ΩR/2). After a Rabi period T = 2π/ ΩR, we have

<b>T = −<b>0 = -A/ħ. Such behavior is the optical analog

of the spin-1/2 system undergoing a 2π rotation in

ordinary space. In addition, if the time delay is t = 2T =

4π/R (i.e., after a 4π Rabi oscillation) then <b>T = −<b>0

= A/ħ: the two signals are now in phase and we have the

corresponding 4π rotation in a spin-1/2 system. We

observe no phase change behavior in <b†b>. The results

in this section show that the simple analytical model here

analyzed contains all the essential physics of the process

including the π phase shift after a complete Rabi-like

oscillation.

Conclusion

In this paper we proposed an all-optical analog of the

well-known sign change of the spinor wave functions

under 2π rotations. The system here investigated consists

of two planar MCs coupled through a central mirror. Here

the two modes (in the absence of coupling) play the role

of the two spin states, whereas the coupling induces a

quasiperiodic exchange of the optical excitation among

the two modes after ultrafast optical excitation. A

complete oscillation of the excitation from one mode to

the other and back is the optical analog of a 2π spin

rotation. We showed that by feeding the coupled-MC

system with a pair of phase-locked probe pulses separated

by precise delay times, we can gather direct information

on the sign change of the transmitted field after one

complete Rabi-like oscillation period. Such results were

explained qualitatively by a simplified physical model

considering two coupled damped oscillators


88

References [1] H. J. Bernstein, Phys. Rev. Lett. 18, 1102 (1967);

[2] Y. Aharonov and L. Susskind, Phys. Rev. 158, 1237 (1967); [3] H. Rauch, A. Zeilinger, G. Badurek, A.Wilfing,W. Bauspiess, and

U. Bonse, Phys. Lett. A 54, 425 (1975);

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[5] A. G. Klein and G. I. Opat, Phys. Rev. D 11, 523 (1975); Phys.

Rev.Lett. 37, 238 (1976); [6] A. Abragam, The Principles of Nuclear Magnetism (Clarendon

Press, Oxford, 1961);

[7] E. Klempt, Phys. Rev. D 13, 3125 (1976); [8] M. P. Silverman, Eur. J. Phys. 1, 116 (1980);

[9] J. M. Raimond, M. Brune, and S. Haroche, Rev. Mod. Phys. 73, 3

(2001);

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57, 14877 (1998); [13] G. Panzarini, L. C. Andreani, A. Armitage, D. Baxter, M.

S.Skolnick, V. N. Astratov, J. S. Roberts, A. V. Kavokin, M.

R.Vladimirova, and M. A. Kaliteevski, Phys. Rev. B 59, 5082 (1999);

[14] S. Vignolini, F. Intonti, M. Zani, F. Riboli, D. S.Wiersma, L.

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[15] 28P. Yeh, Amnon Yariv, and Chi-Shain Hong, J. Opt. Soc. Am.

67, 423 (1977).


89

SPECTRAL DEPENDENCE OF THE AMPLIFICATION FACTOR IN

SURFACE ENHANCED RAMAN SCATTERING

C. D‘Andreaa,b,*

, B. Fazioa, A. Irrera

a, P. Artoni

c, O.M. Maragò

a,

G. Calogeroa and P.G. Gucciardi

a

a) CNR – Istituto Processi Chimico-Fisici, Viale F. Stagno D’Alcontres, 37, I-98158, Messina, Italy

b) Dottorato in Fisica dell’Università di Messina, Dip.to di Fisica, F. S. D’Alcontres, I-98158 S. Agata - Messina, Italy

c) MATIS, CNR - Istituto per la Microelettronica e i Microsistemi, Via S. Sofia, 64, I-95123, Catania, Italy


Abstract

Surface Enhanced Raman Scattering (SERS) is

characterized by a strong signal amplification (up to

108÷10

) when both the excitation and the Raman photons

frequencies match the localized plasmon resonances

(LSPR) of the nanoparticles (NPs). In order to understand

if the effective LSPR profile refers to the bare NPs or to

the resonance of NPs ―dressed‖ with the probe molecules,

we perform multiwavelength (514nm, 633nm and 785nm)

SERS experiments using evaporate gold NPs as SERS-

active substrate on which we deposited Methylene Blue

molecules (MB) that yields a resonance energy red-shift

and a broadening of the LSPR profile.

The SERS spectra at the investigated excitation

wavelengths display a different intensity ratio of the

characteristic MB band (peaks at 450 cm-1

and 1620 cm-1

)

with respect to the Raman counterpart.

In presence of MB molecules, a red shift of 50 nm in

the LSPR is observed

The enhancement of the Raman modes at the different

excitation wavelengths follows a trend similar to the

LSPR profile of the ―dressed‖ NPs, although the

maximum enhancement is found at 785nm excitation, in

spite of a LSPR peak at 600nm.

Introduction

Surface enhanced Raman Scattering (SERS) is an

ultrasensitive spectroscopy technique that allows the

detection of molecules adsorbed on noble metal

nanoparticles (Au, Ag, Cu, etc) at sub-pico molar

concentrations and enables to detect, under optimal

condition, a single molecule [1, 2].

The giant signal amplification of SERS is related to the

collective excitation of nanoparticles (NPs) conduction

electrons, the so-called localized surface plasmon

resonance (LSPR). When the frequency of incident

photons is resonant with the LSPR of NPs, an increase of

the electromagnetic (EM) fields can be obtained in the

region close to the NPs surface, called Hot spots [3]. In

particular, in SERS, when both the excitation and the

Raman photons frequencies (ωL and ωR, respectively) are

resonant with the LSPR of the NPs, the enhancement can

reach 108÷10

order of magnitude as demonstrated

experimentally [4-8] and theoretically, according to the

|E|4 approximation [9,10].

The LSPR profile strictly depends on the size/shape of

the particles, the inter-particle distance, the surrounding

medium [11,12], and the spectral dependence of both the

excitation field enhancement factor Aexc(ω) and the re-

radiation enhancement factor Arad(ω) have been observed

to be proportional to the LSPR profile, Q(ω) [4, 12]. The

spectral dependence of Q(ω) is therefore particularly

important since it determines both the best excitation

wavelength for optimal SERS detection and the re-

radiation enhancement of the Raman modes.

It is still not known, however, whether the effective

Q(ω) refers to the LSPR of the bare NPs or to the

resonance of the NPs ―dressed‖ with the probe molecules

[Qdress(ω)]. The latter is typically energy shifted and can

be much broader, according to the molecular dielectric

constant.

The LSPR profiles can be obtained easily by extinction

spectroscopy, which is the easiest and most powerful tool

to study the resonance energy of metal NPs. Differently

from the extinction spectroscopy that is a far-field

technique, SERS measurements give insight on the

―local‖ near-field (the field in the hot spots) so, detailed

comparison of the SERS enhancement factor (EF) with

the LSPR profiles of SERS-active substrates is a possible

way to understand the properties of the electromagnetic

hot spots in NPs.

To get insight on this phenomenon we carried out

multi-wavelength SERS experiments using evaporated

gold nanoparticles as SERS-active substrates on which we

deposited Methylene Blue molecules that notably alter the

LSPR profile. The SERS peaks intensities, normalized to

the Raman intensities measured on a flat gold region, and

the relative enhancement factor of the Methylene Blue

Raman modes were compared with the LSPR spectra

highlighting an additional frequency shift, not appreciable

in the LSPR profile.

Materials and methods

The gold clusters were prepared by Electron Beam

Evaporation (EBE) on SiO2.The sample was heated at

480°C and a gold amount of 1 1016

cm-2

was evaporated.


90

Figure 3: Extinction spectra of bare Gold

Nanoparticles (black line) and after (blue line) the

binding of the Methylene Blue molecules. The

three colour line and box indicate the excitation

line and the corresponding Raman region of MB

for the three lasers of our apparatus.

Gold atoms arrive on the heated substrate, so they have

the possibility to diffuse over the substrate, immediately

starting a ripening process leading to cluster formation. In

order to promote the adhesion of the gold NPs to the

substrate, the clusters were covered by a thin Silicon

Oxide layer (2-3 nm) produced by RF magnetron

sputtering.

The Methylene Blue (MB) solution was prepared

mixing deionized water with the powder (Carlo Erba

Reagenti) at the concentration of 10-4

M. The samples of

gold NPs were soaked into aqueous solution of dye for

1h, then washed in water and dried in vertical position to

avoid formation of too thick multilayer of molecules on

substrates. This method guarantees that only a single layer

of MB dye remains adsorbed onto the array, as reported in

literature [3,7,13]. Extinction and SERS experiments were

carried out with a HR800 – Jobin Yvon micro-

spectrometer. For the extinction measurements, we

exploiting the white light xenon lamp embedded in the

microscope of the HR800 spectrometer. A 10X objective

was used to collect the light transmitted through the

sample and the HR spectrometer was used to acquire the

optical signal. The LSPR profile was then proportional to

the ratio between the light transmitted in absence (I0) or

in presence of NPs (INPs). For multi-wavelength SERS

measurements we coupled our spectrometer with an Ar++

(515 nm), a He-Ne (633 nm) and a diode (785 nm) laser.

In this back-scattering Raman setup, measurements were

done focusing a few tens of µW of laser power on a

submicron spot using a 100X microscope objective (NA

0.95). All the spectra were acquired with integration times

from 10 to 120 seconds and power over the range from 4

to 400μW.

Discussion

Figure 1 shows the different LSPR profiles between the

bare NPs (blue line) and ―dressed‖ NPs (black line). The

presence of a layer of Methylene Blue molecules bound to

the gold NPs substrate yields a resonance energy red-shift

of about 50 nm (from 570 nm to 620 nm) and a

broadening of 50 nm. By using the several excitation

wavelengths available in the experimental set up, we were

able to excite the ascending and the descending region of

the dressed LSPR profile Qdress(ω) (with 515 nm and 633

nm laser lines), and the out of resonance region (by using

the laser line at 785nm), where we don‘t expect SERS

effect (colour lines in Fig. 1). As shown in figure 1 by the

colour boxes relative to each excitation wavelength, the

Raman spectrum of MB extends in the 400 – 1650 cm-1

region [7, 13] with the most intense peaks at 450 cm-1

and

1620 cm-1

.

According to previous study [14], looking the

extinction profile, for the laser excitation at 515 nm we

can expect a progressive increase of the intensity of the

SERS Raman mode of MB passing from the low

frequencies to the higher, with respect to the Raman mode

in absence of SERS effect. An opposite behaviour is

envisaged for the laser excitation at 633 nm; in this

condition the 450 cm-1

bands are closer to the LSPR peak,

and then to the condition of maximum resonance.

The SERS spectra at the investigated excitation

wavelengths (fig. 2, colour lines) display, as expected, a

different intensity ratio of the 450 cm-1

and 1620 cm-1

peaks with respect to the Raman counterpart. For each

excitation wavelength, in fact, to comparing SERS and

Raman spectra and to calculate the EF, we acquired the

MB Raman modes coming from a flat gold region (fig 2,

black lines). This expedient allowed us, also, to exclude

any contributions linked to chemical bonds between gold

and Methylene blue.

Figure 4: SERS spectra of Methylene blue for 515,

633 and 785 nm excitation wavelength (colour

line) compared with the Raman counterpart

acquired on a flat gold region (black line).


91

At 515 nm (green line) the 1620 cm-1

mode is more

enhanced with respect to the peak at 450 cm-1

, but a

similar trend is also observed for excitation wavelength at

633 nm (red line). This behaviour is not compatible with

the both the LSPR profiles acquired in the extinction

measurements. This trend is extended until the near

infrared region by using an excitation wavelength of 785

nm; here the SERS spectra show a higher enhancement of

the modes at 450 cm-1

than those at 1620 cm-1

.

Comparing the intensity of the principal bands of

Methylene Blue SERS spectra with the corresponding

Raman modes, it was possible to plot the relative mode

enhancement factor versus the Raman shift for each

excitation wavelength, as showed in figure 3. In this

picture is evident the incremental behaviour of the EF for

the visible excitations: at 515 nm we have an

enhancement from 8 times for the low frequency modes,

to 30 for the bands at 1620cm-1

. In the same way, at

633 nm (central box) the modes experience an EF from

220 to 350 times.

Figure 5: Relative SERS enhancement factor for

the 515, 633 and 785nm excitation wavelengths.

The colour lines are guide for eyes.

The maximum EF was obtained for the excitation at

785 nm, and joining 4 orders of magnitude for the bands

at 450 cm-1

, and decreasing of a factor of 10 (until 3

orders of magnitude) for the higher frequency modes.

Thank to the colour lines, guide for eyes, is evident the

new behaviour extrapolated by the SERS spectra: the

maximum enhancement happens for visible-NIR region,

100 nm red shifted with respect to the peak of the LSPR

profile.

The red shift of the near-field peak energies with

respect to the far-field quantities is a well-known

phenomenon in literature. It depends to the size of the

particles, with larger particles displaying a more marked

shift [15], but there is not a complete and simple

explanation in agreement with the experimental data that

can be used for a quantitative prediction of the shift.

This work is a partial study, contribute for the PhD

annual report, but it opens the way for future

measurements and considerations. Our purpose is to

extend the number of excitation wavelength. Using 532,

560, 660 and 695 nm excitation sources we can complete

our multi-wavelength analysis and try to find the exact

position of the maximum EF, since to obtain a complete

profile to compare with the LSPR profile. At the same

time, this experimental data may be of interest for

theoretical calculations in order to clarify the connection

between the far-field and the near-field point of view of

the same effect.

Conclusion

Multi-wavelength SERS measurements were carried

out on SERS active substrates of gold evaporated

nanoclusters. The SERS intensities of the modes of the

probe molecules, the Methylene Blue, were studied and

compared with the corresponding Raman spectra.

Then, the SERS Enhancement Factor behaviour was

compared with the Local Surface Plasmon Resonance

profile of the substrate. The presence of Methylene blue

soaked on gold nanoparticles causes an energy red shift

and a broadening of LSPR profile, as known in literature,

but the maximum enhancement was obtained for an

excitation wavelength in the Near Infrared region

(785nm), in spite of LSPR peak at 600 nm. These results

open the way for further measurements and calculations

for a better understanding about the differences between

near and far field point of view, basics for a proper

comparison between the LSPR and SERS profiles, and

thus for the optimization of the enhancement factors.

Acknowledgments

We acknowledge funding from the EU-FP7-

NANOANTENNA project GA 241818 ―Development of

a high sensitive and specific nanobiosensor based on

surface enhanced vibrational spectroscopy‖ and the PRIN

2008 project 2008J858Y7_004 ―Plasmonics in self-

assembled nanoparticles / Surface Enhanced Raman

Spectroscopy on self-assembled metallic nanoparticles.‖

References [1] S. Nie and S. R. Emory, Science 275 (1997) 1102;

[2] K. Kneipp et al., Chemical Physics 247 (1999) 155; [3] G. Laurent et al., Physical Review B 71 (2005) 045430;

[4] E.C. Le Ru et al. Journal of Physical Chemistry C 112 (2008)

8117;


92

[5] H. Wang et al., Journal of American Chemical Society 127 (2005)

14992; [6] E.C. Le Ru et al., Journal of Physical Chemistry C 111 (2007)

13794;

[7] G. Xiao and S. Man, Chemical Physics Letters 447 (2007) 305; [8] M. Kall et al., Journal of Raman Spectroscopy 36 (2005) 510;

[9] K. Kneipp et al., Chemical Review 99 (1999) 2957;

[10] E.C. Le Ru et al., Chemical Physics Letters 423 (2006) 63;

[11] A. Otto, Journal of Raman Spectroscopy 22 (1991) 743;

[12] E.C. Le Ru et al., Current Applied Physics 8 (2008) 467; [13] S. Nicolai and J. Rubim, Langmiur 19 (2003) 4291;

[14] A. McFarland et al., Journal of Physical Chemistry B 109 (2005)

11279; [15] J. Zuloaga and P. Nordlander, Nanoletters 11 (2011) 1280.


93

PHOTOLUMINESCENCE OF A QUANTUM EMITTER IN THE CENTER

OF A DIMER NANOANTENNA: TRANSITION FROM THE PURCELL

EFFECT TO NANOPOLARITONS

N.Finaa,*, A.Ridolfo

b, O.Di Stefano

a,, O.M.Maragò

c ,S.Savasta

a

a)Dipartimento di Fisica della Materia ed Ingegneria Elettronica,Università di Messina,

Viale F.S. D’Alcontres 31, 98166 , Messina, Italy

b) Technische Universitat Munchen, Physik Department, Germany.

c) Istituto per i Processi Chimico-Fisici, Viale F. Stagno d’Alcontres 37, 98158, Messina, Italy


Abstract

We present a fully quantum mechanical approach to

describe the light emitting properties of strongly

interacting plasmons and excitons. Specifically we

present calculations for ultracompact quantum systems

constituted by a single quantum emitter (QE) (a

semiconductor quantum dot) placed in the gap between

two metallic nanoparticles. Light emitted by the quantum

dot is shown to undergo dramatic intensity and spectral

changes when the emitter excitation level is tuned across

the gap-plasmon resonance. The resulting plexciton

dispersion curve differs significantly from the one

obtained via scattering experiments [1]. Our work

suggests that the strong interaction between metallic

nanoparticles and excitons can exploited for tailoring the

spectral properties of quantum emitters for the realization

of ultracompact colored and white LEDs.

Introduction

The light-matter strong coupling regime is fascinating,

as it allows nonlinear quantum optics experiments to be

done with as few as two photons, control of the direction

of emission or phase of one photon with another one, the

observation of single-atom lasing, the study and

exploitation of quantum entanglement [2].

Here we investigate the emission properties of two

Silver Metal Nanoparticles (MNP) with a Quantum Dot

(QD) between these (see Fig. 1). In particular we study

the modifications of the quantum emitter

photoluminescence (PL) induced by the presence of the

metallic nanoparticles (MNPs). We also study the

transition from the weak to the strong coupling regime.

Fig.1 Dimer nanoantenna with quantum emitter.

Entire system is embedded in an optically active

medium.

Theory

The system is schematically showed in Fig1. It is

entirely embedded in a medium with constant permittivity

bε . The expectation value of the total system polarization

is given by:

mP f a (1)

where a is the destruction operator for the localized

surface SP mode, the QD dipole moment e d ,

and the coefficient f is given in Eq. (10). The term

is the expectation value of the lowering transition

operator eg . The QE and the MNP interacts via

dipole-dipole coupling.

States g e transition is resonantly coupled with

the localized surface plasmon dipole mode with a strength

g, as showed in Fig 2.



94

Fig 2. Quantum emitter two level representation:

external optical pump excites ground QD states,

giving rise to excitonic emission of light caused by

interaction with MNPs-SP.

Electrons are optically or electrically pumped from

lower levels j to upper levels i , then decay

nonradiatively to level e . Electrons finally decay by

spontaneous emission to level e .The full quantum

dynamics of the coupled nanosystem can be derived from

the following master equation for the density operator,

X sp( , )Si H L L (2)

Where SH represents the Hamiltonian terms including

free dynamics, interaction and driving, i.e.:

S 0 int driveH H H H (3)

with

† †

0 sp xH a a (4)

where x and sp are the energies of the QD

excitonic and MNP plasmonic transitions. Eq.(4)

represents the free system Hamiltonian equal to the sum

of free MNP system term with free QE term. The

Hamiltonian term describing the interaction between the

QD exciton and the quantized SP field, in the rotating

wave approximation reads:

† †

int ( )H i a ag (5)

Where:

g (6)

being

3

0

4 6 '

(8 1)Q r (7)

a field term related to the whole system, and, where:

3

3

RQ

S r (8)

with 1, 2 ,S whether the field polarization is

parallel or orthogonal to the R direction [3], while ' is a

parameter depending on SP resonance frequency. The

system excitation by a classical input field can be

described by:

† * †

drive 0 0( ) ( )H E a a E (9)

Notice that 0E is different from zero only in scattering

calculations. The Markovian interaction with reservoirs

determining the decay rates xγ and spγ for the QD

exciton and the SP mode respectively, as well as the

pumping mechanism of the QD, is described by the

Liouvillian terms, XL and spL [4]. Furthermore we

found that the term related to interaction of MNPs-SP

with incoming field is f , and it‘s given by:

3b0

48iQ 2'

(1 8 ) 3f r

Q (10)

Results

We have calculated the PL on a system with a 6nm

radius MNP at a distance R = 9.5 nm embedded in a

medium with a dielectric constant bε = 3.


95

Fig.3 : Calculated dimer nanoantenna-QE PL

spectrum for different dipole moments.

In Fig.3 we can see how, on increasing the QD dipole

moment, the splitting between the two PL peaks enhances

[5]. This is due to the fact that the Vacuum Rabi Splitting

(VRS) limit is given by the following condition:

x sp(γ +γ )2

2g (11)

and, because, from Eq.(6), g is related to dipole

moment, on increasing of it, will increase the VRS, as

shown by PL spectra.

The PL spectra achieved at different distances between

the two MNPs, tuning the exciton frequency on the

resonance MNP-SP frequency, with a dipole moment μ/e

=0.7nm, are shown in Fig.4. We can see how, on

increasing the distance QE-MNP, strong coupling

plexcitonic effect, progressively, vanishes, until to show

only the QD dipole row (on R=28nm).

Fig.4 : PL spectra calculated for different

distances centered at frequency a . On

increasing distances the double peak splitting

disappears. A dipole moment μ/e =0.7nm has been

used.

The influence of MNPs on the PL of quantum emitter

has been studied in the weak coupling regime [7]. Here

we addressed the situation where the interaction between

the emitter(s) and the MNPs is so strong that a

perturbative approach fails. Figure 5 displays a series of

PL spectra taken at different exciton-SP energy detuning.

The typical anticrossing behavior, characteristic of the

strong coupling regime, can be observed. At large

detunings the PL emission is concentrated at the transition

energy of the emitter.


96

Fig.5. PL spectra taken at different exciton-SP

energy detuning.

When the transition energy approaches the SP

resonance, two emission peaks are clearly visible and

emission is shared by the two polariton modes. For

comparison, Fig. 6 shows scattering spectra [6] which

display a different behavior and a different normal mode

splitting.

Fig.6. Scattering spectra as a function of the exciton

resonance.

Conclusions

We have investigated for the first time light emission

properties of QEs strongly coupled to MNPs. When

strong coupling is achieved, light emitted by the QD is

shown to undergo dramatic intensity and spectral changes

when the emitter excitation level is tuned across the gap-

plasmon resonance. The resulting plexciton dispersion

curve differs significantly from the one obtained via

scattering experiments. This work suggests that the strong

interaction between metallic nanoparticles and excitons

can exploited for tailoring the spectral properties of

quantum emitters for the realization of ultracompact

colored and white LEDs.

References [1] A. Ridolfo et al., Phys. Rev. Lett. 105, 263601 (2010);

[2] Kimble, H. J. Strong interactions of single atoms and photons in cavity QED. Phys. Scripta 76, 127–137 (1998);

[3] S.A Maier Plasmonics: Fundamentals and applications, Springer;

[4] M.O. Scully, M.S. Zubairy, Quantum Optics, Cambridge Univ.press;

[5] G.Khitrova et al. Nature Physics 2, (2006); [6] S.Savasta et al., ACS Nano 4 (11)(2010), pp. 6369 6376

[7] L.Novotny,B.Hecht, Principles of Nano-Optics, Cambridge

Univ.pres


97

LATERAL DIFFUSION OF DPPC AND OCTANOL IN A

LIPID BILAYER MEASURED BY PFGE NMR SPECTROSCOPY

S. Rificia,*

a)Dottorato in Fisica dell’Università di Messina, Dip.to di Fisica, F.S. D’Alcontres ,98166 S. Agata-Messina, Italy


Abstract

Lipid lateral diffusion coefficients in the system of 1,2-

palmitoyl-sn-glycero-3-phosphocholine (DPPC), Octanol

and water were determined by the pulsed field gradient

NMR technique on macroscopically aligned bilayers. The

molar ratios between DPPC and Octanol and between

DPPC and water were set to 1:2 and 1:28 respectively.

The temperature was varied between 270 K and 323 K.

Introduction

Cell membrane is the first part of the cell to be in

contact with any nutrient or pathogen in the extracellular

matrix. Biological membranes are complex mixtures of

different lipid molecules and proteins. A lipid is an

amphiphilic molecule with an hydrophilic polar

headgroup and usually two hydrophobic hydrocarbon

chains. When dispersed in an aqueous environment, lipids

self-assemble in order to reduce contacts with water. They

can arrange themselves in a variety of morphologies

depending on the structure of the lipid, the nature of the

lipid headgroup and its degree of hydration, temperature,

concentration and osmotic pressure. Multilamellar

vesicles, continuous ordered bilayers and monolayers,

liposomes and micelles are typical examples of possible

structural arrangements. [1]

Single artificial phospholipid, or simple mixtures of

artificial phospholipids have long been used as mimetic

membranes for examining the physical, chemical and

biological properties of the biomembranes. This approach

is justified by the observation that some model membrane

systems have been widely recognized as essentially

equivalent to natural systems such as those found in

myelin and erythrocyte membranes. [2]

Dipalmitoylphosphatidylcholine (DPPC) has a very

simple chemical structure, a phosphocoline (PC)

headgroup and two identical linear saturated hydrocarbon

chains, and plasma membrane contains a relatively large

amount of phospholipids with PC headgroup, this is why

DPPC is so largely used in all studies about model

membrane. Despite it has been widely studied, his

dynamics are still not well understood.

Many structural and dynamic intrinsic properties of

aqueous dispersions of lipid bilayers are governed by

temperature. In the case of phosphatidylcholines, these

phase transitions take place within the temperature range

263–353 K, depending on the strength of the attractive

Van der Waals interactions between adjacent lipid

molecules. Longer tailed lipids have more area to interact,

increasing the strength of this interaction and

consequently decreasing the lipid mobility. Transition

temperature can also be affected by the degree of

unsaturation of the lipid tails. An unsaturated double bond

can produce a kink in the alkane chain, disrupting the

lipid packing. This disruption creates extra free space

within the bilayer which allows additional flexibility in

the adjacent chains. [3]

DPPC shows three kinds of structural changes with

increasing temperature under atmospheric pressure. This

changes are thermotropic phase transitions: the sub-

transition from the lamellar crystal (Lc) phase to the

lamellar gel (Lβ′) phase, the pre-transition from the Lβ′

phase to the ripple gel (Pβ′) phase, and the main transition

from the Pβ′ phase to the liquid crystalline (Lα) phase

occur in turn with increasing temperature. [4]

The (Lα) phase is considered the most important,

because many biologically relevant processes occur in

this phase. Indeed, lamellar bilayers in the fluid phase

supply an efficient, planar permeability barrier, which still

allows functional flexibility and lateral diffusion motions

of associated membrane proteins.

Adsorption of alcohol molecules or other small

amphiphilic molecules in the cell membrane has a

destabilizing effect on its structure. Experiments on

phospholipid membranes have shown that alcohol

molecules can induce the interdigitated phase [5] that, at

high alcohol concentrations, replaces the ripple gel phase

[6,7]. A complete interdigitation is expected at alcohol

concentrations above a threshold value assumed to be

about 2:1 alcohol to lipid ratio in the membranes as it has

been observed for DPPC/n-butanol system by a DSC

study [7]. When the interdigitation occurs, lipid molecules

from opposing monolayers interpenetrating, thereby

decreasing the bilayer thickness. The increase of the polar

headgroup area, due to the addition of alcohol molecules,

gives rise to a reduction of the Van der Waals attraction

between lipid acyl chains. Bound alcohol molecules

reduce the mobility of the polar headgroups and, at the

same time, cause a decrease of the ordering and an

additional coiling of the melted acyl chains.

Concerning dynamics, different types of motions, with

correlation times ranging from picoseconds

(corresponding to the motion of lipid chain defects, for

example) to microseconds (corresponding to collective

excitations of the bilayer membrane), characterize


98

bilayers, a large variety of which is essential for the

functionality of membranes [8,9,10].

Motions within the bilayer plane have been largely

studied by NMR relaxation techniques [11,12,13] and

neutron scattering [8,9,10].

Experimental details - Sample preparation

The phospholipid 1,2-palmitoyl-sn-glycero-3-

phosphocholine (DPPC) was purchased from Avanti

Polar Lipids, Octanol was purchased from Sigma Chem.

Co. Both chemicals were used without further

purification.

Aligned multilayers of DPPC with Octanol were

obtained following the preparation suggested by Hallock

[14], using mica plates as supporting substrate. Mica

substrate was covered with about 1.5 mg of lipids per

cm2. Following the cited procedure, DPPC and Octanol

were dissolved in an excess of 2:1 CHCl3/CH3OH

(chloroform/methanol). The solution was spread and dried

on the face of the substrate plate. All procedures for

sample preparation were executed in a glove box under

nitrogen gas to prevent lipid oxidation. This procedure

resulted in a thin film covering the whole area of the mica

plate. The sample was indirectly hydrated at 323 K in

96% relative humidity using a saturated potassium sulfate

D2O solution for 12 days, after which 28 mole of D2O per

mole of lipid were added. The mica plate was then placed

in a glass tube in the diffusion probe.

Nuclear magnetic resonance

Self diffusion coefficients of hydration water ( WD ),

DPPC ( D ) and Octanol ( OcD ) molecules were

measured by hydrogen pulsed-field gradient spin echo

NMR (1H-PGSE-NMR), which enables the non-invasive

measurement of molecular self diffusion coefficient over

a wide range of time scales (from milliseconds to

seconds) directly [15, 16].

PGSE experiments were performed on aligned pure

DPPC and DPPC with Octanol membranes deposited on

mica sheets. All measurements were carried out in fully

hydration condition at temperatures below, near and

above the phase transition temperature using a Bruker

AVANCE NMR spectrometer operating at 700MHz 1H-

resonance frequency. The temperature was controlled

within ± 0.5 K by a heated air stream passing the sample.

Self-diffusion measurements are based on NMR pulse

sequences, which generate a spin-echo of the

magnetization of the resonant nuclei. The method is based

on sensitising the sample to molecular translational

displacement by the application of magnetic field-

gradient pulses.

By the appropriate addition of two pulsed-field

gradients, in the defocusing and refocusing period of the

sequence, of duration δ and intensity g, separated by a

time interval Δ, the spin-echo intensity becomes sensitive

to the translational motion along the gradient direction for

the tagged molecules. These gradients, in fact, cause the

nuclear spins in different local positions in the sample to

precess at different Larmor frequencies, thereby

enhancing the dephasing process. If the spins maintain

their positions throughout the experiment, they will still

refocus completely into a spin–echo by the SE pulse

sequence. On the other hand, if they change their

positions during the experiment, their precession rates

will also change, and the refocusing will be incomplete,

resulting in a decrease in the intensity of the spin–echo.

The spin echo M(δg,Δ), is attenuated according to

2

0/ exp[ ]M M DQ (1)

where Q g and γ is the gyromagnetic ratio of 1H. Q

has the dimension of an inverse length, being a measure

of the spatial scale probed, and is equivalent to the

exchanged wave vector in a scattering experiment.

In our experiment, the mica plate with deposited DPPC

with Octanol is placed parallel to the magnetic field to

test for lateral (in-plane) diffusion. To record the decay of

the 1H components, a train of pulses at increasing gradient

strength is used.

Integration of spectral peaks was performed using the

Bruker-supplied XWIN-NMR software.

Figure 1 shows the decay of spin-echo intensities for

water and phospholipid/alcohol system as a function of

Q2Δ for three different temperatures, T=287K (triangle),

T=291K (circle) and T=295K (square). In the same

figures, the fitting curves (continuous lines), obtained

from a nonlinear fit of the Fourier-transformed peak

amplitudes according to the Equation (1), are also shown.

The data were fitted to an equation with three diffusion

coefficients. This would be the case for a system

consisting of three separated species. In fact, three decay

times are clearly visible, the faster due to water

molecules, the lower to phospholipid molecules, and the

intermediate ascribed to Octanol molecules.

The found diffusion coefficients for WD , D and OcD

are reported in Table 1.

Table 1

T=287K T=291K T=295K

2 /WD m s 103.4 10 103.8 10

105.1 10

2 /OcD m s 116.5 10 117.1 10

101.3 10

2 /D m s 127 10 125.3 10

111 10


99

1E8 1E9 1E10 1E11

0.1

1

DPPC+Octanol

M /

M0

Q2 Delta [m

2 sec]

T=287 K

T=291 K

T=295 K

Fit

Figura 1: PGSE intensity decay in fully hydrated

DPPC/Octanol bilayer at T=287K (triangle),

T=291K (circle) and T=295K (square). The

continuous lines are the fitting functions.

In the case of water molecules, we found diffusion

coefficients in good agreement with those measured in

PC-water systems, which are in the range of 10 21 10 /m s to

10 220 10 /m s depending on water

concentration, temperature, and bilayer composition. [17,

18,19,20,21,22].

Figure 2 shows the three diffusion coefficients as a

function of T.

It can be observed that the lateral diffusion coefficient

increases with increasing temperature; i.e. when the full

system is clearly in the liquid–crystalline phase, where

enhanced dynamics of the acyl chains are expected.

Water and alcohol molecules follow membrane

transition. Alcohol diffusion sharply lowers near the main

transition temperature, and, below the transition, it seems

that alcohol and DPPC molecules have the same diffusion

coefficient. Below the transition, Octanol and DPPC

move together, and this is an evidence of the formation of

the interdigitated phase.

Conclusions 1H-PGSE-NMR experiments provided information on

long-range lateral diffusion, up to some mm distances, of

inter-layer water, lipid and Octanol molecules.

Three decay times are clearly visible, the faster due to

water molecules, the lower to phospholipid molecules,

and the intermediate ascribed to Octanol molecules.

In the case of water, a reduction in the diffusion

coefficient alone is observed and assigned to restricted

geometry.

On the other hand, the phospholipid component shows

a novel and interesting result of a nearly constant

diffusion coefficient in the gel phase and a net increase in

mobility in the liquid–crystalline phase.

275 280 285 290 295 300 305 310 315 320

0.0

2.0x10-10

4.0x10-10

6.0x10-10

8.0x10-10

1.0x10-9

1.2x10-9

D (

m2/s

ec)

T(K)

DW

DOc

D

Figura 2: The three self diffusion coefficients of

hydration water (circles), DPPC (stars) and

Octanol (triangles) as a function of T are shown.

The self diffusion coefficient of bulk water (empty

circles) in also plotted.

Below the transition, Octanol and DPPC move

together, and this is an evidence of the formation of the

interdigitated phase.

References [1] R. Lipowsky and E. Sackmann, Handbook of Biological Physics,

Vol. 1, Elsevier Science, Amsterdam, 1995; [2] Rosser, M. F. N., H. M. Lu, and P. Dea. 1999, Biophys. Chem.

81:33–44;

[3] R. Koyonova and M. Caffrey, Biochim. Biophys. Acta 1376 (1998) p.91;

[4] N Tamai, M Goto, H Matsuki, S Kaneshina, Journal of Physics:

Conference Series 215 (2010) 012161 doi:10.1088/1742-6596/215/1/012161;

[5] J. L. Slater and C. H. Huang, Prog. Lipid Res. 27, 325-359 (1988);

[6] E. S. Rowe, T.A. Cutrera, Biochemestry 29, 10398-10404 (1990); [7] F. Zhang and E. S. Rowe, Biochemistry 31, 2005-2011 (1992);

[8] M.C. Rheinstadter, T. Seyde, L. Demmel et al., Phys. Rev. E 71 (2005) p.061908;

[9] M.C. Rheinstadter, C. Ollinger, G. Fragneto et al., Phys. Rev. Lett.

93 (2004) p.108107; [10] S. Konig, W. Pfeiffer, T. Bayerl et al., J. Phys. II (1992) p.1589;

[11] S. Konig, T.M. Bayerl, G. Coddens et al., Biophys. J. 68 (1995)

p.1871; [12] G. Oradd and G. Lindblom, Biophys. J. 87 (2004) p.980;

[13] P. Meier, E. Ohmes and G. Kothe, J. Chem. Phys. 85 (1986)

p.3598;

[14] Hallock K J, Henzler Wildman K, Lee D K and Ramamoorthy A

2002 Biophys. J. 82 2499–503;

[15] E.O. Stejskal and J.E.Tanner, J. Chem. Phys. 42 (1965) p.288; [16] H.V. As and P. Lens, J. Ind. Microbiol. Biotech. 26 (2001) p.43;

[17] Lange, Y., and C. M. Gary Bobo. 1974, J. Gen. Physiol. 63:690-

706; [18] Inglefield. P. T., K. A. Lindblom, and A. M. Gottlieb. 1976,

Biochim. Biophys. Acta. 419:196-205;

[19] Lindblom, G., H. Wennerstrom, and G. Arvidson. 1977, J. Quant. Chem. 12(2):153-158;

[20] Chan, W. K., and P. S. Pershan. 1978, Biophys. J. 23:427-449;

[21] Konig, S., E. Sackmann, D. Richter, R. Zorn, C. Carlile, and T. M. Bayerl. 1994, J. Chem. Phys. 100:3307-3316;

[22] Volke, F., S. Eisenblatter, J. Galle, and G. Klose. 1994, Chem.

Phys. Lipids. 70:121-131.


100


101

CHEMICAL EQUILIBRATION OF THE QUARK GLUON PLASMA

F.Scardinaa,b,

*, M.Colonnab, V.Greco

,b,c, M.Di Toro

b


b) INFN Laboratori Nazionali del Sud, Via S. Sofia 62, I-25125 Catania, Italy

c) Dipatimento di Fisica e Astronomia, Università di Catania, Via S. Sofia 64, I-95125 Catania, Italy


Abstract

The ultra-relativistic heavy ion collisions performed at

the Relativistic Heavy Ion Collider (RHIC) and at Large

Hadron Collider (LHC) represent the fundamental tool to

study the properties of the Quark Gluon Plasma (QGP).

We have studied the evolution of the QGP created in such

collisions using a relativistic transport code which is

based on the solution of the relativistic Boltzmann

equation including elastic and inelastic two body

collisions between partons. We have focused our attention

on the chemical equilibration of the QGP. In fact such

equilibration is a fundamental step to deal with before to

analyze hadronization. We have performed calculation in

a box at equilibrium in order to check the code and finally

we have performed simulation for the collision in both

RHIC and LHC case. The purpose of our work is to show

how the QGP, which is initially composed for mostly by

gluons, go towards chemical equilibrium with a

consequent enhancement of the quarks number. Moreover

we have studied the dependence of the chemical

equilibration from the transverse momentum pT. We have

observed that at the end of the evolution of the fireball

the ratio Nq/Ng in the region of low pT reach the

equilibrium value of 2.25. The presence of a such large

amount of quarks should modify the background for the

various energy loss scenarios. The ratio between the

quark number and the gluon number in the region of high

pT do not reach the equilibrium value but is significantly

different from the initial value. This difference should

explain the relative abundances of the hadrons that

coming from the fragmentation of high pT partons.

INTRODUCTION

We have studied the evolution of the QGP created in

ultra-relativistic heavy-ion collision with a relativistic

transport code based on the numerical solution of the

relativistic Boltzmann. Using such code we have studied

the chemical equilibration of the QGP created at RHIC

and at LHC. The analysis of such equilibration assume a

fundamental importance in order to have a comprehension

of the abundances of the different species of hadrons

revealed in the experiment. Moreover we want to improve

the description of the QGP using an effective kinetic

theory for a quasi-particle model. In such model the

particle acquire an effective mass and this causes a

further enhancement of the quark number.

TRASPORT APPROACH

We have studied the evolution of the Quark Gluon

Plasma using a relativistic transport simulations based on

the solution of the Boltzamann equation.

22( , )p f x p C (1)

Where f(x,p) are the partons distributions functions and

C22 is the collision term.

' '

3

222 3

1 2

3 ' 3 '' '1 2

1 2 1 23 ' 3 '

1 2

24 4 ' '

1 2 1 212 12

1 1

2 (2 ) 2

( )(2 ) 2 (2 ) 2

(2 ) ( )

d pC

E E

d p d pf f f f

E E

M p p p p

(2)

υ is set equal to 2 if 1 and 2 are identical particles.

For the implementation of the collision integral we use

the so called stochastic algorithm[1,2]. In such algorithm

if the collision will happen or not is sampled

stochastically comparing the probability of the two body

collision with a random number between 0 and 1.

2 2

22 22 3

1 2

collrel

N tP v

N N x (3)

If the extracted number is less than the probability the

collision will occur. In the limit Δt ->0 Δx->0 the

numerical solutions using the stochastic method converge

To the exact solution of the Boltzamann equation. So it

is important to divide the space into sufficient small cells.

We consider both elastic and inelastic collision using

the differential cross section indicated in the following

formulas [1,3]

2

2 2 2 2

2

( )

gg gg

s

T T D

d

dq q q (4)


102

2

2 2 23 ( )

gg qq

s

T T q

d

dq s q m

(5)

2

2 2 2

64

27 ( )

gg qq

s

T T q

d

dq s q m (6)

Where qT is the transverse component of moment

transfer, mD and mq denote respectively the Debye mass

for gluons q and quarks respectively.

Calculations In a Box at equilibrium

With the purpose of demonstrate the correct operation

of our code we have chosen some situation in which the

outcome are known analytically. Hence we have

performed ―box calculations" in which a particle

ensemble is enclosed in a box, with fixed limits, and

evolve dynamically until an appropriate final time.

Initially particles are distributed homogeneously within

the box and their momentum is chosen highly anisotropic

( 6 ) ( )T z

T z

dNp GeV p

Ndp dp (7)

After a sufficiently long time the system equilibrate as

shown in fig. 1. For a classical, ultrarelativistic ideal gas

the energy distribution has the Boltzmann form

/

2 3

1

2

E TdNe

NE dE T (8)

In figure 1 the time evolution of the energy distribution

for such box calculations is depicted the size of the box is

125 fm3. We have considered anisotropic calculations and

we have taken a constant cross section of mb. The

final time is 3 fm/c. Moreover in order to improve

statistics we have used 50 test particles for one real. The

dotted line in the figures indicate the analytical

distribution with temperature T=2 GeV calculated using

The following formula

3 T (9)

Where the energy density and the particle densities are

given by the initial conditions. We see a good agreement

between the numerical results and the analytical

distributions.

As we can observe from the figure our code reproduce

analytical results. In order to have sufficient argument to

guarantee whether our algorithm operating correctly is

necessary to check other quantity, as for example the time

evolution of momentum anisotropy shown in fig. 2 and

defined as the average transverse momentum squared

over the average longitudinal momentum squared. The

initial conditions in this case are set to be the same as in

fig 1.

Figure 1:Temporal evolution of energy distribution

of a system consisting of N=2000 massless

particle in a fixed box whose size are 125 fm3

Figure 2: Time evolution of the momentum anysotopy

from box calculations. The initial conditions are set to be

the same as in Fig. 1

Once we have checked that our algorithm reproduce the

analytical calculation relatives to kinetic equilibrium we

have checked that also the chemical equilibrium of the

plasma can be reproduced by our algorithm.

For massless case the ratio between the number of

quark and the number of gluon is simply given by the

ratio between the respective degrees of freedom υ

q q

g g

N

N (10)


103

where υq=2*3*Nf υg = 2*8. In our case we consider two

flavour and thus the ratio between the number of quark

and the number of gluons is 2.25. The results are shown

in fig.3

Figure 3:Time evolution of the gluon and quark

number in box calculations. We have considered

gluons and quarks with three flavour as parton

species

Results for the heavy Ion collision

We have performed simulations for heavy-ion

collisions for both RHIC (200 AGeV) and LHC (5.5

ATeV). In figure 4 are shown the ratio between the

number of quark and the number of gluons as a function

of transverse momentum. The dot line indicate the initial

ratio while the thick line and the dashed line indicate the

final ratio obtained at RHIC and LHC respectively. We

can observe that for both RHIC and LHC at low

transverse momenta the ratio is near to the equilibrium

value. Moreover at LHC where the evolution time is

longer also at high pT the ratio is different from the initial

one

Figure 4: Ratio between the quarks number and

the gluon number as a function of pT

EFFECT OF THE MEAN FIELD

We have the intention to introduce in our code the

effect of the mean field using a quasi-particle model [4].

In such a model the interaction is encoded in the quasi

particle masses and once the interaction is accounted for

in this way the quasi particle behave like a free gas of

massive constituents.

The effect of the masses on the chemical equilibration

of the plasma is substantial.

In the massive case the ratio Nq/Ng depends on the

temperature as can be calculated in the following formula

2

2

/

2

2

/

q

g

q T

q qm T

q q

g gg T

g gm T

md e

TN

N md e

T

(11)

Where

2 2 2 21 1;q q g gm p m p

T T (12)

The expected ratio is indicated in fig. 5. In this figure

we can observe that the value of the ratio is strongly

dependent from temperature and that at the freeze-out

temperature the ratio reach the value of 6.3 that is larger

that the value obtained in the massless case.

Figure 5: ratio Nq /Ng as a function of temperature

calculated using the formula 0.8

Conclusions

The Quark Gluon Plasma created in heavy-ion

collisions seem to reach chemical equilibrium at low

transverse momentum, but in the case of LHC also at

high pT the ratio is significantly different from the

initial one. Thus at the end of its evolution the number


104

of quark in the plasma is greater than the number of

gluons and this have two important implication: first of

all the background of the energy loss process is

significantly modified and moreover the abundances of

the different species (pion, proton , kaon) coming from

the fragmentation of quarks and gluons are significantly

affected by the increasing of the quarks number. In the

region of high transverse momenta this effect must be

analyzed in order to have a better comprehension of

the different suppression experienced by the hadronic

species and have to be compared with the results of the

[5,6,7].

We have moreover the intention to include the effect of

the mean field in order to give a better description of

the QGP. This will be done using a quasi-particle

model.

We expect that the effect of the masses will increase the

ratio between the quark number and the gluon number

up to 6 for the region of low pT . This implicate that the

bulk should be for mostly composed by quarks.

REFERENCES

[1] Z. Xu , C. Greiner, Phys. Rev C.71 (2005) 064901;

[2] G. Ferini , M. Colonna, M. Di Toro and V. Greco, Phys. Lett. B

670, 325 (2009); [3] J. F. Owens, E. Reya, and M. Gluck, Phys. Rev. D 18, 1501

(1978);

[4] S. Plumari, W M. Alberico, V. Greco, C. Ratti, arXiv :1103.5611 [hep-ph];

[5] F. Scardina, M. Di Toro, V. Greco, Phys. Rev. C 82 (2010)

054901; [6] W. Liu, C. M. Ko and B. W. Zhang, Phys. Rev. C 75 (2007)

051901;

[7] F. Scardina, M. Di Toro, V. Greco, Nuovo Cim. C34N2 (2011) 67-73.


105

A STUDY ABOUT DYNAMIC MODELS ON PHOSPHOLIPIDS

A. Trimarchia,*



Abstract

Model membranes are a first step to understand very

complex objects like cell membranes. The former

constitute a essential element so that cells work.

Membranes are active protagonists in many processes, as

material transport and cell signaling. The comprehension

of the dynamics in play can give us the possibility to

exploit them in several research fields like pharmaceutical

industries or medical sciences. In this paper we try to

explain some membrane motions by applying several

models to the elastic incoherent scattering factor (EISF)

like the spherical diffusion or the uniaxial rotation and we

show the results.

Introduction

Membranes are an essential part of the living organisms,

playing a fundamental role in several tasks[1]: they

surround cells separating them from the external

environment. They are composed of amphipathic

phospholipids: a hydrophilic head and one or two

hydrophobic chains. In a biological membrane there are

many different types of lipids as well as many other

components besides them, like the proteins, that have

important tasks as surface recognition, cytoskeleton

contact, signaling, enzymatic activity, or transporting

substances across the membrane. Membranes are an

important site of cell-cell communication. The complexity

of these objects makes their study very difficult so we

approximate them with more simple structures,

phospholipid bilayers. Phospholipids undergo phase

transitions in the temperature range from -10 to 80 °C; the

main phases belonging to bilayers are the gel phase where

the chains are stiff and well ordered, and the liquid phase

where the chains are quite disordered. The structures that

these phospholipids can form are several ones, depending

on lipid concentration, temperature, pressure, and the

presence of other substances: they can form bilayer

structures, spherical structures, like liposomes, or

micelles[2,3]. Dimensionally, important structural

quantities to characterize a phospholipid bilayer are the

lamellar repeat spacing D, the hydrocarbon chain

thickness 2Dc and the average area per lipid A. NMR, X-

ray and neutron diffraction[4-6] techniques provided

several information about form factors, electron density

and scattering length density profiles, while further

information and confirmations to experimental models are

been obtained by simulations[7]. Nowadays membranes

are objects of studying for several research fields and

applications[8,9]. In this paper we focus our attention on a

QENS study of DMPC(1,2-dimyristoylsn-glycero-3-

phosphatidylcholine), and POPC (1-palmitoyl-2-oleoyl-

sn-glycero-3-phosphocholine) phospholipid bilayer, in

order to investigate dynamics.

Experimental details

SAMPLE PREPARATION

DMPC and POPC powder sample were purchased from

Avanti Polar Lipids. The samples were prepared in order

to obtained aligned multilayers following the preparation

suggested by Hallock et al.[10]. The lipids were dissolved

in a solution 2:1 CHCL3/CH3OH (chloroform/methanol).

After drying the lipid solution, it was joined to a solution

2:1 CHCL3/CH3OH containing a 1:1 molar ratio of

naphthalene (C10H8) to lipid so that for each mg of

substrate the lipid was dissolved again in 15 μl of this

solution. This solution was applied on only one face of

the mica sheets, so that we spreaded about 1,5 mg of lipid

per cm2. Naphthalene and any residual organic solvent

were removed by means of a vacuum drying overnight.

Hydration at 40 °C in 96 % relative humidity was

indirectly performed using a saturated potassium sulfate

D2O solution for 12 days, after which 28 moles of D2O

per mole of lipid are added. Each sample was then built

up stacking 6 substrate plates piled with the last foil not

spreaded, and was equilibrated at 4 °C for 12 additional

days. The alignment was then verified by 31

P-NMR

chemical shift and with X-ray diffraction.

SPECTROMETER

The IN5, time of flight (TOF) spectrometer, at ILL

Facility (Grenoble), has been used to perform neutron

scattering measurements on the phospholipids.

This instrument is used to study low-energy transfer

processes as a function of momentum transfer, typically,

in the region of small energy and momentum transfer

values, with an energy resolution of the order of δE/E =

1% (e.g. quasi-elastic scattering in solids, liquids,

molecular crystals and inelastic scattering with small

energy transfers in the order of magnitude 0.1-250 meV).

It is characterized by a primary spectrometer in which two

synchronized choppers are used to define the incident

beam energy, while a third chopper removes unwanted

neutrons. A fourth chopper, finally, turning with lower

velocity, avoids different pulse overlap. Samples, usually,

were run in two orientations for the normal to membrane

plane and beam direction.


106

At θ = 135°, the dynamics are mainly probed in the

membrane plane. All scans have been performed starting

from an equilibrated liquid crystalline phase hydrated

with 28 D2O molecules per lipid.

Figure 6:Data fits of DMPC sample at 307 K and

POPC sample at 298K in 135° orientation. Data

have a resolution of 37μeV. Spectra representation

is in logarithmic scale to better display

lorentzians.

DATA ANALYSIS

Experimental data have been collected on IN5 at a

resolution of 37 μeV and with a wavelength λ =8Å. We

have measured DMPC+28 D2O multi bilayer sample at T

= 307 K and POPC+28 D2O multi bilayer sample at T =

298 K and both are in liquid phase. Both measurement

have been performed in the 135° orientation that gives us

information about in-plane motions. Treatment data have

been executed with LAMP software, in order to remove

bad spectra, correct cross-sections and rebin in energy the

time of flight obtained data; afterwards they have been

fitted by performing a linear least-square analysis and

using Minuit program.

The line shape is well represented by the sum of a Delta

function and three Lorentzian functions convoluted with

the instrumental resolutions. We have assumed as fit

parameters the areas of the four functions and the half

width at half maximum (HWHM) of the three lorentzian

curves:

21 2 2 2

2

3 43 42 2 2 2

3 4

( ) ( )I A A

A A

(1)

It is interesting to notice that this model fits very well

the experimental data as it is clear from the Figure 1

where a semi logarithmic plot is displayed to put the

emphasis on residues.

From fit parameters of DMPC and POPC it is evident

as the A1, the area of the Gaussian curve (Figure 2), is

decreasing with Q. This means that in both case, the

dynamics is confined. Furthermore, the HWHMs of the

two phospholipids shows us three different dynamics

belonging to systems, in so far occur on different time-

scales and the specific rates of each one differ from other

ones at least an order of magnitude (Figure 3).

From the areas with several mathematical passages, we

can obtain the EISFs of the three motions for the two

systems; in particular the fast motion EISF can be

obtained easily like 1-A4. Several models can be used to

fit these quantities and obtain information about dynamics

concerning the sample and its spatial displacement.

Figure 2: POPC areas: the A_1 component (Delta

contribution) highlights a confined dynamics.

EISFs have been fitted with suitable models by means

of Mathematica® software.


107

Figure 3:HWHM of the three motions. Diffusion

(dark points) and rattling motion (blue points).

EISF corresponding to the first lorentzian with HWHM

= 10-12 µeV can be considered to belong to a diffusion

of the atoms around their position[11]. The motion

characterized by a HWHM of about 2000 µeV is believed

to be a fast rotation, called also rattling motion around the

molecule axis. The model applied to the corresponding

EISF is the uniaxial rotation model[12]:

2 2

0

(2 1) ( ) ( )m m

m

EISF m j QR S (2)

where

0

( )2sinh

(cos )exp( cos )

m

m

S

P d

(3)

is an order parameter e Pm is the Legendre polynomials

of order m.

The δ parameter provides information about how the

motion of the atom has a distribution in a direction:

greater the parameter, more directional the

distribution[13]. A limit case is δ = 0 that corresponds to

an uniform distribution.

The EISF concerning the HWHM of about 100 µeV is

not quite clear yet, and other studies are requested to give

it an accurate meaning.

For the experimental setup specifications, free diffusion

of lipids is too slow to be observed, and it is hidden inside

the experimental resolution. In literature, there are several

models to explain these motions. The slow motion is

considered like a diffusion in a restricted volume or, or

like a ballistic motion with a long range transport on a

nanometre scale with a Gaussian-like model[14-16]. The

fast motion is considered like a rattling motion [15], while

the intermediate dynamics is thought like a kink motion, a

combination of a rotation plus an out of plane

diffusion[14].

Experimental results

From the above relations the shape of the three EISF

can be determined (Figure 4).

A comparison between POPC and DMPC EISFs (in

particular in Figure 5 diffusion EISF) shows as for all

three motions the POPC structure factors are always

higher than DMPC ones. This means POPC is

characterized by a dynamics slower than DMPC one;

hypothesis about this experimental fact can be ascribed to

acyl chains more long in the POPC, and then a more

molecular weight; the presence of a double bond between

carbon atoms in one of this POPC chain could likely

entail a decreased mobility of the whole system.

Figure 4: EISF of the motions concerning the

hydrogen atoms of the fatty acid chain of POPC.

The EISF corresponding to rattling motion is displayed

in Figure 6 with the fit curve. The formula (2) was cut off

after sixth order to calculus limits of the computer used to

run Mathematica. The value of R in the formula was

inserted like a constant and equal to the C-H bond length:

R = 1.1 Å. The formula was modified with the adding of a

normalization parameter, A, to have at Q = 0 Å-1

an

unitary value of EISF. The model fits quite well both

EISF samples and provides for the parameters the

following values; for DMPC sample, δ = 2.45, A =

0.1997, while for POPC sample, δ = 1.95, A = 0.248. In

the case of DMPC, the experimental points from Q = 1,4

Å-1

to 2.2 Å-1

have been adding from DMPC data obtained

in an experiment with wavelength λ = 5 Å. The fit results

tell us that the distribution is quite uniform, in particular

for the DMPC sample.


108

Figure 5: EISF comparison between POPC and

DMPC samples

Figure 6: Fit of the EISF of the rattling motion

with the uniaxial rotation model.

Conclusion

This work has highlighted like our phenomenological

model fits very well experimental data bringing out the

presence of three distinct motions that involve hydrogen

atoms of the phospholipidic hydrophobic chains: an

hampered rotation, that we can indicate like a rattling

motion, of the hydrogen atom around its position. The

other two motions need further studies and the application

of other models to be identify with more clarity. The

phenomenological model which we have proposed to fit

data has provided similar results to other ones available in

bibliography[13-18]. The uniaxial rotation model applied

to the EISF of the rattling motion gave us information

about its distribution width. Successive studies will deal

with investigations in normal direction to the membrane

(45° orientation) and evaluations of these motions at

different temperatures to observe, i. e., how dynamics

behaves in the gel phase. A further study will take in

consideration the interdigitation of alcohols between

phospholipids in order to observe their influence on this

system.

References [1] R. Lipowsky, E. Sackmann. (1995) Structure and Dynamics of

membranes: from cells to vesicles. Handbook of Biological

Physics, Vol 1;

[2] Jain, M., Introduction to Biological Membranes, 2nd ed.,

John Wiley & Sons, New York, 1988;

[3] Gennis, R.G., Biomembranes. Molecular Structure and

Function, Springer-Verlag, New York, 1989; [4] G. Buldt et al., J. Mol. Biol., 134, 673, 1979; [5] G. Zaccai et al., J. Mol. Biol., 134, 693, 1979;

[6] J. N. Sachs et al., Biophys. J., 100, 2112, 2011;

[7] I. Z. Zubrzycki et al., J. Chem. Phys., 112, 3437, 2000;

[8] Immordino ML, Dosio F, Cattel L., Int. J. Nanomedicine 1 (3)

(2006) 297–315;

[9] Dagenais, C. et al., Eur. J. Phar. Sci., 38(2) (2009) 121-137; [10] K. J. Hallock et al., Biophys. J., 82, 2499, 2002;

[11] V. F. Sears, Can. J. Phys. 45, 237 (1967);

[12] B. F. Mentzen, Mater. Res. Bull., 1987, 22, 337; [13] M. Bee, Quasielastic Neutron Scattering; Taylor & Francis: 1988;

[14] Sackmann, E., Konig, S., Pfeiffer, W., Bayerl, T., Richter, D., J.

Phys. II France 2 (1992) 1589-1615; [15] Busch, S., Smuda, C., Pardo, L. C., Unruh, T., J. Am. Chem. Soc. ,

2010, 132 (10), pp.3232-3233;

[16] Konig S., Sackmann E., Richter D., Zorn R., Carlile C., Bayerl T. M., J. Chem. Phys. 100 (1994) 3307-3316;

[17] Konig, S., Bayerl, T. M., Coddens, G., Richter, D., Sackmann, E.,

Biophys. J. 68 (1995), 1871-1880;

[18] Pfeiffer, W., Henkel, T., Sackmann, E., Knoll, W., Richter, D.,

Europhys. Lett., 8 (2), pp. 201-206 (1989).


109

ULTRAFAST OPTICAL CONTROL OF LIGHT-MATTER INTERACTION

AND OF WAVE-PARTICLE DUALITY

Rocco Vilardia,*, Salvatore Savasta

a

a ) Dipartimento di Fisica della Materia e Ingegneria Elettronica, Università di Messina, I-98166 Messina, Italy


Abstract

A recent article [1] theoretically demonstrated the

possibility of an ultrafast control of the wave-particle

duality. It exploits a three-level quantum system strongly

coupled to a resonant microcavity. The proposed ultrafast

optical control can be experimentally realized availing

oneself of many different quantum systems ranging from

Cooper pair boxes to intersubband polaritons, from

semiconductor quantum dots to atomic physics. By

sending an opportune sequence of external probe and

control pulses it is shown that it is possible to induce a

fast coherence sudden death but also it‘s a coherence

sudden birth.

Here we theoretically study that process in deeper

detail demonstrating that the lost first order coherence is

transferred to higher order coherences. Thanks to this

process it is, therefore, possible to successively recover

first order coherence.

We also discuss a new homodyne-like scheme which

exploits phase-locked probe pulses in order to

experimentally study the wave-particle duality of the

considered quantum system and wave particle duality is

easily probed just revealing the photons escaping the

microcavity.

Introduction

The principal aim of quantum information science and

technology is the control over the modalities of

interaction between single photons and individual

quantum emitters [2-4]. Thanks to the usage of

microcavities, under opportune experimental conditions

the strength of the interaction between the quantum

emitter and the electromagnetic interaction cavity field

can be so intense that light quanta can be absorbed and

reemitted many times before escaping the cavity [2,5-9].

In such cases the physical system enters strong coupling

regime under which hybrid light-matter quasiparticles

arise.

Nowadays strong coupling can be achieved and

exploited in many experimental physical system ranging

from circuit QED [10,11] to atomic systems [12], from

quantum dots [13] in optical microcavities to microcavity

embedded quantum wells [14]. Moreover, recent studies

show the possibility to achieve the so called ultra strong

coupling regime. For all these systems, it is important to

be able to switch to and from weak coupling regime and

to be able to control the time evolution of coherences.

A recent article points out the possibility to ultrafast

switch on and off the strong coupling regime depending

on the order and on the particular times at which pulses

are sent [1]. In particular it is demonstrated that not only

some internal degrees of freedoms can be in strong

coupling while others are in weak coupling regime but the

same degree of freedom can show a mix of both weak

coupling and strong coupling features. Another important

achievement of such an article is the demonstration of an

ultrafast technique for erasing the first order photonic

coherence explaining such a phenomenology in terms of

the fundamental quantum complementarity principle

directly connected to the information one can achieve

about the quantum physical system.

In such an article it is studied the same quantum system

discuss in [1]: a single-mode microcavity containing a

quantum emitter modeled as a three level fermionic

system. The center of the presented research is the study

of the modalities of exchange of information between

different internal degrees of freedom of the same quantum

system and the study of a particular way for controlling

and testing the wave-particle duality.

In order to conduct our studies we availed ourselves of

computational simulations and of a analytical

calculations.

Theoretical model

The point of reference of our theoretical study is the

master equation for the density operator

[ , ]i H L (1)

where the total Hamiltonian H is

0 I inH H H H (2)

being

†

0 ,

,1,2

j j j a

j g

H a a (3)

†

1,2 . .IH g a H c (4)

and

* *

,1( ) ( ) . .in p c gH t a t H c (5)


110

a and , respectively are the

destruction operator for the single cavity mode and the

transition operator of the levels of a quantum emitter.

( )p t represents a Gaussian coherent probe pulses

resonant both with the g e transition and with the

single cavity mode. ( )c t is a control pulse resonant

with the s g transition (see the schemes in figure

1)

The realized computational simulations the adopted

parameters are: light-matter coupling constant

85g eV , cavity damping 20a eV , damping

of the ―g‖ level 2g eV , damping of the ―e‖ level

5e meV , pure dephasing of the ―g‖ level

0d

g eV , pure dephasing of the ―e‖ level

0d

e eV , 2 2.28e g meV .

Figure 1 left: The quantum emitter is theoretically

represented by the following three level scheme.

The fundamental quantum state is s . The first

and the second excited states respectively are g

and e : they respectively are the ground state

and the first excited state of the g e transition

energetically and strongly coupled to the probe

pulse. On the other hand, the s g transition is

energetically resonant with the control pulse.

Figure 1 right: Microcavity scheme. The quantum

emitter (green sphere) is placed within the

microcavity which can be externally pumped with

probe and control pulses.

Transfer of coherence

In order to study the temporal evolution of the general

quantum state we imposed that the initial quantum state is

0 s : the microcavity is empty while the quantum

emitter is in its fundamental state. A probe pulse is sent

to the microcavity. Because it is energetically resonant

with the single cavity mode, the cavity photon population

abruptly reaches a maximum after which it monotonically

decays due to cavity losses. A control pulse is sent in

correspondence to the second successive minimum.

Because it is energetically resonant with the s g

transition, its arrival determines the complete population

of the ―g‖ level. Because of the fact that g e transition

is energetically resonant and strongly coupled to the

single cavity mode than the cavity photon population †a a shows characteristic vacuum Rabi oscillations

which are also showed by the squared modulus of its

coherent part 2

a . By sending another identical

control pulse in correspondence to a minimum of †a a ,

†a a continues to perform its oscillations while 2

a

vanishes. As explained in [1] such behaviour is

explainable thanks to the fundamental quantum

complementarity principle (see figure 2).

Figure 2: (Panel a) After the first control pulse

both the cavity photon population †a a (black

dotted line) and the squared modulus of its

coherent part 2

a (continuous red line)

immediately raise for then monotonically decays

due to cavity losses. After the first control pulse

strong coupling starts and both begin to oscillate.

Cavity photon population continues to oscillate

also after a second control pulse sent in

correspondence to a minimum. On the other hand, 2

a vanishes. (Panel b) Where 2

a vanishes

2

sga oscillates. Before the second control

pulse such coherence was zero but for a short time

in correspondence to the arrival of the first control

pulse.

The zeroing of the 2

a poses a natural question.

Where does the information relative to the first order


111

photonic coherence go? Is it lost? Is it transferred? And

whereto? For trying to investigate such problematic, it is

useful to send a third identical control pulse in

correspondence to a minimum of †a a . The cavity

photon population continues to exhibit vacuum Rabi

oscillations while the 2

a shows a sudden rebirth and

begins to oscillate too. Such phenomenology clearly

highlights the fact that the lost-and-then-found first order

coherence is transferred to other internal degrees of

freedom. The question is now: ―Where is it transferred?‖

A detailed analysis of higher order coherences allows to

find the answer. There exist a coherence which is zero

before the arrival of the second control pulse and after the

third (it is not zero for a small time in correspondence to

the first control pulse) and which oscillates between the

second and the third control pulse. Such coherence is 2

sga . The amplitude of its oscillation is exactly that

2

a would have showed if it would have not suddenly

died due to the arrival of the second control pulse.

This analysis leads to the conclusion that 2

a and

2

sga exchange their behaviour. In other words, the

information relative to 2

a is transferred to other

internal degrees of freedom (see figure 3).

Figure 3: If a third control pulse is sent in

correspondence to the minimum of the cavity

photon population then †a a continues to

oscillate while 2

a shows a sudden rebirth and

2

sga suddenly dies.

The transfer of coherence is a general mechanism.

Sending, for example, the third control pulse in

correspondence to maximum of the cavity photon

population, †a a begins to monotonically decay and

2

a remains zero. In this case, the coherence is

transferred to 2

sga before the first control pulse

while, after it, it is transferred to 2

sga which exhibit

a monotonic decay. Such a behaviour is really important

because it testifies that the transfer of coherence takes into

consideration the effects of the modifications induced by

external pulses (see figure 4).

Figure 4: If the third control pulse is sent in

correspondence to the maximum of the cavity

photon population then †a a monotonically

decays, 2

a continues to be zero, 2

sga

oscillates between the second and the third control

pulse and the 2

sga monotonically decays

after the third control pulse.

Homodyne test of wave-particle duality

a is not a physical observable. For this reason, in

order to study such property we need indirect

measurement. To this end, it is possible to exploit an

homodyne technique by which ultrafast testing the wave-

particle duality exploring an additional degree of

freedom: a relative phase between two phase-locked

probe pulses sent after an initial control pulse [14,15].


112

2

1

2

2

2

2

( )( ) exp( ) exp

2

( )exp[ ]exp

2

P a

t tt A i t

t tB i

(6)

After a control pulse and a successive first probe

pulse at 2 0.14at , the cavity photon population

rapidly raises and soon after beginning to oscillate. If a

second probe pulse is sent in correspondence to a

maximum of †a a at 2 0.88at with a relative

phase 0 destructive interference is observed. If,

instead, the relative phase is constructive

interference is observed. If between the two phase-locked

probe pulses it is sent a control pulse then no interference

is observable (see figure 5).

Figure 5:A control pulse is followed by two phase-

locked probe pulse. After a second probe pulse

sent with a relative phase 0 , destructive

interference is observed. If the relative phase is

then constructive interference is obtained. If

between the two phase-locked probe pulse it is

sent a control pulse then no interference is

observed.

In other words, thanks to homodyne-like measurement we

can access to information relative to inference also in a

physical observable which intensity is. After having

observed what happens in three specific cases in which it

was imposed that the relative phase is either zero or ,

we studied the phenomenology with a continuous

variation of the relative phase (see figure 6 and 7).

Figure 6: (Left) The probe pulse is sent at the first

cavity photon population maximum and

intereference is seen in the degree of freedom.

(Right)The same happens if the second probe

pulse is sent at the second cavity photon

population maximum. but for a phase with

respect to that showed in figure 6 left and in

agreement with [16].

The three three-dimensional figures thus obtained clearly

testify the presence or absence of interference in the

degree of freedom.

Figure 7: No interference is observed if a control

pulse is sent betweeen a the two probe pulses.

If the second control pulse is sent in correspondence to

a cavity population maximum then 0ec t

2 2( ) 1 0gt c t g d t s (7)

The temporal evolution operator †

pU b a1 is such

that the general quantum state after the first three pulses is

2

( ) 1 0

1 0

g

t

p e

t c t g d t s

d t b e s c t e

(8)

Noticing that i

p pb b e it follows that the

information relative to the phase degree of freedom is

connected only to the coefficient 1 s . If the quantum

emitter is in its ―g‖ state then light is connected to the first


113

probe puse. If the quantum emitter is in the ―e‖ level than

the light is connected to the second probe pulse. In other

terms, monitoring the state of the quantum emitter we

acquire the which-way information about the origin of the

photon and, therefore, due to fundamental quantum

complementarity principle, interference disappears. On

the contrary, if the second control pulse is not sent than it

is not possible to get such information and, therefore,

interference manifests itsself.

Conclusions

The presented researches explains the reason why

sudden death and sudden ribirth of coherence happen

highlighting that the information relative to a coherence

can be transferred to other internal degrees of freedoms of

the considered physical system. Such achivement is

connected to the possibility to experimentally control in

an ultrafast way the trasfer of information within a certain

physical system thus paving the way to technological

quantum information advancements.

At the meanwhile, these studies explain the way to

ultrafast ontrol wave-particle duality thanks to a

homodyne-like detection scheme. The studied scheme

could find easy experimental realization thanks to its

simplicity.

References [1] A. Ridolfo, R. Vilardi, O. Di Stefano, S. Portolan, and S. Savasta,

Phys. Rev. Lett. 106, 013601 (2011); [2] J. M. Raimond, M. Brune, S. Haroche, Rev. Mod. Phys. 73, 565

(2001);

[3] C. Monroe, Nature (London) 416, 238 (2002); [4] L. M. Duan and H. J. Kimble, Phys. Rev. Lett. 92, 127902 (2004);

[5] C. Weisbuch, M. Nishioka, A. Ishikawa, and Y. Arakawa, Phys.

Rev. Lett. 69, 3314 (1992); [6] J. P. Reithmaier, G. Sek, A. Löffler, C. Hofmann, S. Kuhn, S.

Reitzenstein, L. V. Keldysh, V. D. Kulakovskii, T. L. Reinecke,

and A. Forchel, Nature (London) 432, 197 (2004); [7] T. Yoshie , A. Scherer, J. Hendrickson, G. Khitrova, H. M. Gibbs,

G. Rupper, C. Ell, O. B. Shchekin, and D. G. Deppe, Nature

(London) 432, 200 (2004); [8] K. Hennessy, A. Badolato, M. Winger, D. Gerace, M. Atatüre, S.

Gulde, S. Fält, E. L. Hu, and A. Imamoglu, Nature 445, 896

(2007); [9] I. Chiorescu, P. Bertet, K. Semba, Y. Nakamura, C. J. P. M.

Harmans, and J. E. Mooij, Nature (London) 431, 159 (2004);

[10] A. A. Abdumalikov, O. Astafiev, A. M. Zagoskin, Yu. A. Pashkin, Y. Nakamura, and J. S. Tsai, Phys. Rev. Lett. 104, 193601 (2010);

[11] B. Peropadre, P. Forn-Diaz, E. Solano, and J. J. Garcia-Ripoll,

Phys. Rev. Lett. 105, 023601 (2010); [12] J. McKeever, A. Boca, A. D. Boozer, J. R. Buck, and H. J. Kimble,

Nature 425, 268, (2003);

[13] A. Dousse, Jan Suffczyński, , A. Beveratos, O. Krebs, A. Lemaître, I. Sagnes, J. Bloch, P. Voisin and P. Senellart, Nature (London)

466, 217, (2010);

[14] O. Di Stefano, A. Ridolfo, S. Portolan, and S. Savasta, Opt. Lett. 36 No.22, (2011);

[15] R Vilardi, A. Ridolfo, S. Portolan, S. Savasta, O. Di Stefano,

Quantum Complementarity of Cavity Photons Coupled to a Three-Level System, to be published by Physical Review A.;

[16] O. Di Stefano, R. Stassi, A. Ridolfo, S. Patanè, and S. Savasta,

Phys. Rev. B, 84, 085324 (2011).


114


115

SEMINARI (Invited)

DEL DOTTORATO DI RICERCA

IN FISICA

Effettuati nel 2011


116

Dottorato di Ricerca in Fisica dell’Università degli Studi di Messina 19 Gennaio 2011, ore 15.00, Aula E. Majorana, Dip.to di Fisica

V.le F. Stagno d‘Alcontes 31, Messina

Prof. Józef SURA Heavy Ion Laboratory (HIL), University of Warsaw, Poland

Seminar title:

The HIL Cyclotron and associated ion optics

Abstract The isochronous cyclotron of the Heavy Ion Laboratory of Warsaw accelerates ions with mass to charge

ratio in the range of A/Q=(2-6) and energies up to 30 MeV per nucleon.

The design of this setup includes many of the accelerator physics and ion optics elements.

These elements beginning with the ECR ion source, injection, acceleration, extraction, beam lines, till

the experimental setups will be discussed.

________

Dottorato di Ricerca in Fisica dell’Università degli Studi di Messina 7 Febbraio 2011, ore 15.00, Aula E. Majorana, Dip.to di Fisica

V.le F. Stagno d‘Alcontes 31, Messina

Dr. Ernesto Amato Dipartimento di Scienze Radiologiche,

Policlinico dell‘Università di Messina

Seminar title:

The Geant4 Monte Carlo package from Cern and its applications to nuclear, particle,

astroparticle and medical radiation physics

Abstract Geant4 (Geometry and Tracking 4) is a Monte Carlo toolkit developed by Cern in object-oriented C++

programming paradigm, for the simulation of nuclear and particle interaction.

It offers a wide set of complementary physics models, based either on theory or on experimental data

and parametrizations, for electromagnetic and hadronic interactions in energy ranges spanning from

some tens of eV to TeV, together with models for nuclear excitation, fission and decay. Extensions to

low energy interactions and also to optical photon propagation are available.

Complex geometries can be defined and managed, made from elements or compounds whose properties

can be obtained from databases or user defined. Volumes can be made ―sensitive‖ to simulate detectors,

through the use of hits and digitisation classes.

Primary particles propagate through the defined geometry according to the tracking and stepping rules,

obeying to the physics models adopted and to the selected cuts.

Interaction tracks and cascades can be visualized either online or offline, and relevant quantities are

scored in 1-2-3D histograms and n-tuples. Several ancillary softwares from Cern and from application

developer teams aid the user in the I/O phases.

After a general introduction to the Geant4 concept, architecture and physical models, I will comment

on the different fields of application, spanning from the high energy physics and astrophysics

experiments, to the application of radiation physics for dosimetry and radioprotection from sources of

photons, leptons and hadrons.


117

Dottorato di Ricerca in Fisica dell’Università degli Studi di Messina

22 Febbraio 2011, ore 15.00, Aula E. Majorana, Dip.to di Fisica,

V.le F. Stagno d‘Alcontres 31, S. Agata, Messina

Prof. C.A. Squeri, Prof. V. Candela, Dott. J. Trombetta, Dott. A. M. Roszkowska Ophthalmology Unit, Department of Surgical Specialties, University Hospital of Messina,

Messina, Italy.

Seminar title: “Clinical applications of the different laser platforms in ophthalmology”

Abstract: The purpose of this seminary is to present the clinical applications of the different lasers in

ophthalmology. The following lasers will be presented:

Femtosecond lasers. This kind of lasers is characterized by ultrashort pulses. They perform horizontal or vertical corneal cuts

and are used in corneal and refractive surgery. They are adopted in corneal lamellar keratoplasty and in

refractive surgery.

Excimer laser and solid state laser. The characteristics of these lasers are used to modify the anterior corneal shape. Flattening or

steppening of the corneal surface permit to correct existing refractive errors, so such lasers are widely

used in corneal refractive surgery.

Argon laser and diode laser These lasers perform retinal photocoagulation. They create retinal scars with effect on retinal

pathologies such as diabetic retinopathy, retinal ruptures or holes and degenerations.

NdYAG laser. It is above all a disruptive laser used to treat secondary cataract performing posterior capsulotomy. It

is also adopted to resolve an angle closure glaucoma by localized iridotomy (puncture-like openings

through the iris without the removal of iris tissue). ________

Dottorato di Ricerca in Fisica dell’Università degli Studi di Messina 4 Marzo 2011, ore 10.00, Conference Room CNR-IPCF


Seminar title: Ettore Majorana and the Birth of Autoionization

Ennio Arimondo

Dipartimento di Fisica “E. Fermi”, Università di Pisa

Abstract: In some of the first applications of modern quantum mechanics to the spectroscopy of

many-electron atoms, Ettore Majorana in 1931 solved several outstanding problems by developing

the theory of autoionization. Later literature makes only sporadic references to this accomplishment.

After reviewing his work in its contemporary context, we describe subsequent developments in

understanding the spectra treated by Majorana, and extensions of his theory to other areas of

physics. We find several puzzles concerning the treatment of Majorana's work in the subsequent

literature and the way in which the modern theory of autoionization was developed.

The relevant papers are those numbered 3 and 5 in the convenient collection, Ettore Majorana

Scientific Papers: On the occasion of the centenary of his birth, ed. G. F. Bassani et al. (SIF,

Bologna 2006), where they are accompanied by English translations and commentary. The originals

are, respectively, ``I presunti termini anomali dell'elio,"E. Majorana, Il Nuovo Cimento, 8, 78 (1931)

and ``Teoria dei tripletti P' incompleti," E. Majorana, Il Nuovo Cimento, 8, 107 (1931).


118

Dottorato di Ricerca in Fisica dell’Università degli Studi di Messina 24 marzo, alle ore 15.00 nella sala conferenze del CNR di Messina


Seminar Title: Optical Properties of Carbon-based Materials

Elefterios Lidorikis Department of Materials Science & Engineering, University of Ioannina, Ioannina GR-45110 Greece

Abstract: Carbon nanotubes (CNTs), and more recently graphene, have been at the center of

nanotechology research, with the search for new technologies based on their mechanical and

electrical properties ever increasing. Graphene, a two-dimensional honeycomb lattice of carbon

atoms, can be thought of as the ―building block‖ of other carbon allotropes: it can be ―wrapped‖

into fullerenes, ―rolled‖ into CNTs or ―stacked up‖ into graphite, with many of their properties

deriving from graphene.

In this presentation we discuss different aspects of the photonic response of graphene and CNTs.

After a brief introduction to the basic electronic structure and optical properties of graphene, we

discuss recent advances in understanding interference-enhanced (IERS) and surface-enhanced

Raman scattering (SERS) phenomena in graphene. Especially in terms of SERS, graphene provides

the ideal prototype two-dimensional test-material for its investigation. We discuss recent SERS

experiments on graphene and develop a quantitative analytical and numerical theory for its

description.

Next, we investigate the photonic properties of two-dimensional CNT arrays for photon energies up

to 40eV and unveil the physics of two distinct applications: deep-UV photonic crystals and total

visible absorbers. We find three main regimes: for small intertube spacing of 20-30nm, we obtain

strong Bragg scattering and photonic band gaps in the deep-UV range of 25~35 eV. For

intermediate spacing of 40-100nm, the photonic bands anti-cross with the graphite plasmon bands

resulting into a complex photonic structure, and a generally reduced Bragg scattering. For large

spacing >150nm, the Bragg gap moves into the visible and decreases due to absorption. This leads

to nanotube arrays behaving as total optical absorbers. These results can guide the design of CNT-

based photonic applications in the visible and deep UV ranges.

________ Dottorato di Ricerca in Fisica, Università di Messina

Avviso di Seminario 30 Marzo 2010, Ore 15.00, aula E. Majorana, Dipartimento di Fisica, Università di

Messina, V.le F. Stagno D‘Alcontres 31, S. Agata, Messina

Prof. Avazbek NASIROV Bogoliubov Laboratory of Theoretical Physics of the Joint Institute for Nuclear Research of Dubna

(Russia)

Seminar title: "The role of the entrance channel in study of fusion-fission reaction mechanisms "

Abstract: Evaporation residues and binary fragments are main products of the heavy ion collisions at

beam energies around the Coulomb barrier.

The new superheavy elements Z=110-118 are the evaporation residues after emission of neutrons from

the heated compound nucleus which is formed in the complete fusion of projectile and target nuclei.

Due to very small cross section of the synthesis of superheavy elements it is convenient to study the

reaction mechanism by the analysis of fusion-fission fragments formed at fission of compound nucleus.

But the fusion-fission fragments are mixed with the quasifission and fast fission fragments which are

formed without formation of compound nucleus. In this seminar we will discuss the mechanisms and

contributions of these three fissionlike processes to help experimentalists at the choice of reactions for

the synthesis of new superheavy elements.


119

Dottorato di Ricerca in Fisica dell’Università degli Studi di Messina 14 Aprile 2011, ore 15.00, Aula E. Majorana, Dipartimento di Fisica


Seminar title:

Nuclear Energy: how does it work?

Dr.ssa Marina Trimarchi

Dipartimento di Fisica, Università di Messina

Abstract: The possibility to produce energy from nuclear transmutations is a consequence of the

Einstein‘s equation, stating the equivalence between mass and energy.

Fission reactions represent a very powerful energy source, showing a yield 2 millions higher than

that of fossil fuels, without greenhouse gases emission.

Nuclear power plants working principles will be illustrated, with particular attention to safety

aspects, in operational mode as well as in case of accident. In particular, differences between

various generations reactors will be stressed, starting from old RMBK type (Chernobyl) to the

newest EPR type. Other correlated aspects, as nuclear waste disposal and non-proliferation of

nuclear weapons will be considered.

Finally, due to recent event regarding Fukushima nuclear accident, an overview of the actual

nuclear risk and its consequences worldwide will be given. ________

Dottorato di Ricerca in Fisica dell’Università degli Studi di Messina

5 Maggio 2011, ore 15.00, Aula E. Majorana, Dip.to di Fisica,


Dr.ssa Valentina Venuti Dipartimento di Fisica, Universita’ di Messina, CNISM, UdR Messina, Viale Ferdinando Stagno

D’Alcontres 31, P.O. BOX 55, 98166 Messina, ITALY. Email: [email protected]

Seminar title:

Vibrational dynamics and chiral recognition in Ibuprofen/ -cyclodextrins inclusion complexes:

FTIR-ATR and numerical simulation results

Abstract Cyclodextrins are supramolecular host systems able to encapsulate molecules in their hydrophobic

cavity via noncovalent interactions. Their chiral recognition properties, not fully characterized yet, are

of great relevance in pharmaceutical industry.

Here, we studied how the vibrational properties are affected by the chiral recognition process, upon

selection of the non-steroidal anti-inflammatory drug Ibuprofen (IBP) in its chiral (R)- and (S)-, and

racemic (R, S)- forms, as model guest, and native and modified -cyclodextrins ( -CDs) as model host.

The changes induced, as a consequence of complexation, on the vibrational spectrum of IBP, have been

studied, in solid phase, by attenuated total reflection Fourier transform infrared FTIR-ATR. The

recorded spectra have been compared with the wavenumbers and IR intensities as obtained by

simulation for the free and complexed guest molecule. By the temperature-dependent analysis of the

vibrational spectra in the C=O stretching region, the complexation mechanism has been discussed. It

turned out to be enthalpy-driven, with enantiomers of IBP giving rise to more stable inclusion

complexes with respect to the racemate. This combined experimental-numerical approach gave crucial

information on the expected different ―host-guest‖ interactions that drive the chiral recognition process,

helpful to put into evidence differences in the conformational properties of the complexes, that are

retained a prerequisite for chiral recognition.


120

Dottorato di Ricerca in Fisica dell’Università degli Studi di Messina 14 Giugno 2011, ore 12.00, Aula E. Majorana, Dip.to di Fisica,


Dr.ssa Mariapompea Cutroneo Dottorato di Ricerca in Fisica, Università di Messina

Seminar title:

“High Energy proton/ion beams production by sub-ns, kJ-laser plasma interaction”

Abstract The purpose of this seminar is to present some preliminary results recently obtained in the European &

International Experiment, directed by Prof. L. Torrisi of Messina University, at the PALS Laboratory of

Prague (Czech Republic), under the support given by LASERLAB Europe.

Particularly will be presented some preliminary results concerning the plasma generation in forward

direction through thin laser irradiated targets, the plasma laser acceleration of protons and ions at

energies above 1 MeV, the new detection technique employing Thomson parabola and semiconductor

SiC detectors in time-of-flight configuration, and the first measurements of D-D nuclear fusion induced

by 4 MeV deutons accelerated by the laser-plasma.

The original results and experimental approaches will be discussed in view of a more details

descriptions that will be given in the specific scientific Journals.

________



Seminar title: Electron correlations in metals: Dynamical mean-field theory

Václav Janiš Institute of Physics, Academy of Sciences of the Czech Republic,Prague

Abstract Electrons in metals feel only a screened, short-range Coulomb repulsion. In most of the transition

metals, lanthanides and actinides electron correlations are not negligible. To describe the correlation

effects correctly one needs a reliable description of strong electron correlations. Gross features of weak

excitations of the ground state of interacting fermions are described by Fermi-liquid theory. To assess

collective phenomena with quantum coherence in heavy metals, it is necessary to go beyond the

framework of Fermi liquid. The way to go systematically beyond Fermi-liquid theory is offered by the

so-called Dynamical Mean-Field Theory. We review in this talk the underlying ideas of the dynamical

mean-field theory originating in the single-impurity Anderson model and the Kondo effect. We further

discuss various aspects of presently the most advanced theory of strongly correlated electrons with

examples of its application in model and realistic calculations of electronic properties of metals.


121



Seminar title: Electrical conductivity and charge diffusion in disordered solids

Václav Janiš Institute of Physics, Academy of Sciences of the Czech Republic,Prague

Abstract: Electrical resistivity (Ohm‘s law) in solids is caused by the scattering of almost free conduction

electrons on impurities and irregularities in the periodic lattice. The basic theoretical tools for

description of quantum transport are linear response theory and Kubo formulas. We review in this talk

many-body and Green function methods of calculation of the impact of scatterings of electrons on

randomly distributed impurities in metals. We stress the necessity of renormalizations of the

perturbation expansion in the strength of the impurity potential and of consistency between one- and

two-electron Green functions dictated by conservation laws, electron-hole symmetry and and gauge

invariance of the electromagnetic system. Finally we discuss disorder-driven metal-insulator transitions

due to discharging of the Fermi energy and due to vanishing of diffusion in the limit of strong

randomness.

_______



Seminar title:

Il contributo Light-by-Light al momento magnetico anomalo del muone.

Stato attuale e prospettive future.

D. Moricciani INFN, Sezione di Roma \Tor Vergata", I-00133 Roma, Italy


122

Dottorato di Ricerca in Fisica dell’Università degli Studi di Messina 7 Luglio 2011, ore 15.00, Aula E. Majorana, Dip.to di Fisica,


Seminar title:

MESON PHOTOPRODUCTION AT GRAAL AND MAMBO

Dott.ssa R. Di Salvo

INFN Sezione di Roma Tor Vergata

Abstract Meson photoproduction on the nucleon is a powerful tool for the understanding of the nucleon

structure and of the baryon resonances involved in the reaction process. Polarized photon beams, in

combination with large solid angle apparata and/or high precision spectrometers, allow to access

polarization observables, which are particularly sensitive to the properties of baryon resonances, such as

parity and spin. Some of the main results of the GRAAL experiment in Grenoble and the future plans

for the MAMBO experiment, which is presently under construction in Bonn, will be shown and

discussed in detail.

________

Dottorato di Ricerca in Fisica dell’Università degli Studi di Messina 11 Luglio 2011, ore 15.00, Aula E. Majorana, Dip.to di Fisica,


Seminar title:

Thomson parabola spectrograph in investigations of MeV energy ions from laser plasma ion

sources

Andriy Velyhan Institute of Physics, ASCR, Na Slovance 2, 182 21 Prague 8, Czech Republic

Abstract

Laser ion sources (LIS) already have found a wide applications in areas such as material modification,

ion implantation, pulsed laser deposition. LIS can deliver ions with ionization states from Z= 1 up to 55,

and energies ranges from hundreds of eV up to several MeV. Investigations of the interaction of laser

radiation with solid targets is possible by using of Thomson parabola spectrograph (TPS). The operation

principle of the TPS is based on the gradual passage of ions through parallel electric and magnetic

fields. It is an excellent device, which is capable to give a general overview of the charge states and of

the velocity (kinetic energy) distributions of all type of ions produced in a single laser shot only.


123

Dottorato di Ricerca in Fisica dell’Università degli Studi di Messina 28 Settembre 2011, ore 15.00, Aula E. Majorana, Dip.to di Fisica, V.le F. S. d‘Alcontres 31, S. Agata,

Messina; Seminar title: “Laser-generated plasma and its applications”; Dr. Francesco Caridi,

Physics Ph.D. ; Facoltà di Scienze MM. FF. NN., Univ. di Messina, Viale F. S. d’Alcontres, 31 – 98166

– Messina, Italy ;INFN-Sez. CT, Gr. Coll. di Messina, Viale F. S. d’Alcontres, 31 – 98166 – Messina

Plasma production by laser ablation (PLA) of solid targets in vacuum is a topic of growing interest for

many applications in different fields, such as diagnostics techniques, ion acceleration, nuclear physics,

material processing and cultural heritage. Key plasma parameters, such as equivalent temperature,

density, acceleration voltage, ion charge state and fractional ionization, are evaluated using appropriate

diagnostics instruments, such as ion collector, ion energy analyzer, mass quadrupole spectrometer,

optical spectroscope. These tools give us essential information to understand the mechanism of non-

equilibrium plasma development and kinetics. A special interest of PLA concerns the ion acceleration

with high-electrical fields generated in sub-millimeter space by hot and dense laser-generated non

equilibrium plasmas. This new method of producing ion beams is more appealing than classical

techniques that use large accelerator facilities, and, recently, it has been investigated in order to develop

a new generation of laser ion sources (LIS). Furthermore, when extremely intense laser beams interact

with deuterated targets, D-D nuclear fusion reactions can be achieved in hot and dense plasmas. Many

laboratories are using PLA in order to grow thin films as coverage of different substrates. The film

properties, such as stoichiometry, roughness, grain size, crystallinity and porosity, can be modified on

the basis of the used laser wavelength, pulse intensity, pulse width, substrate nature, irradiation

environment conditions, etc. The technique is useful in many scientific fields, such as microelectronics,

chemistry, biomedicine and metallurgy. Laser Ablation coupled to Mass Quadrupole Spectrometry

(LAMQS) is a new technology recently developed for the depth profile and compositional analysis of

different solid materials placed in vacuum. It is very helpful in the field of cultural heritage in order to

compare their composition and morphology and to identify their origin and the type of manufacture. ________

Dottorato di Ricerca in Fisica dell’Università degli Studi di Messina 18 Ottobre 2011, ore 15.00, Aula E. Majorana, Dip.to di Fisica, V.le F. S. d‘Alcontres 31, S. Agata,

Messina; Seminar title: Electroencephalographic signal processing: the use of Independent

Component Analysis and its application to complex motor task. Dr.ssa Simona Lanzafame University of Messina, Department of Matter Physics and Electronic Engineering.

The City College of New York, CUNY, Sophie Davis School of Medicine.

Electroencephalographic (EEG) signal obtained from scalp electrodes is a sum of the large number of

neurons potentials. The interest of the scientific community is in studying the potentials in the sources

inside the brain and not only the potentials on the scalp, which globally describe the brain activity.

The recovery of the exact cortical distribution of an EEG source region is limited by the unsolved of the

inverse source localization problem. For example, far-field potentials from two synchronously active but

physically opposing cortical source areas – e.g., source areas facing each other on opposite sides of a

cortical sulcus – may cancel and their joint activity will have no effect on the scalp data. An ideal goal

for EEG analysis should be to detect and separate activities in multiple concurrently active EEG source

areas, regardless of their relative straights at different moments. A new approach to finding EEG source

activities has been developed based in a simple physiological assumption that across sufficient time, the

EEG signals arising in different cortical source domains are temporally independent of each other. This

means that measuring the scalp EEG activity produced in some of the source domains at a given

moment allows no inferences about EEG activities in the other source domains at the same instant. This

insight and the resulting algorithms for signal separation that have emerged in the last decade have

created a new field within signal processing in general, known in particular as independent component

analysis (ICA). We will discuss the important findings obtained by a novel application of the ICA

algorithm to complex motor task.


124

Dottorato di Ricerca in Fisica dell’Università degli Studi di Messina 14 Novembre 2011, ore 15.00, Aula E. Majorana, Dip.to di Fisica, V.le F. S. d‘Alcontres 31, S. Agata,

Messina; Seminar title: Fukushima: Eight months after ; Dr.ssa Marina Trimarchi

Dipartimento di Fisica, Università di Messina e INFN – Gruppo Collegato di Messina

Abstract The accident occurred at the Fukushima Daichi NPP as a consequence of the Japan Earthquake and

Tsunami, classified at 6th level of the INES, has involved a significant release of radioactive materials,

inducing a considerable contamination and irradiation risk to people and environment.

Actually the short term consequences typical of a nuclear accident can be considered quite overcome,

although the recovery process of the reactors of Fukushima Daichi NPP is a slow and difficult process,

still requiring continuous and arduous efforts from TEPCO workers and Japanese volunteers.

For what concerns the long term risks due to this nuclear accident, a comprehensive understanding of

the contamination status of the environment is necessary to choose the suitable countermeasures to

adopt. In this framework, Japanese government is still providing an astonishing effort in evaluating

contamination and exposure data, that are continuously and correctly shared not only with the scientific

and government institutions involved, but also with the public. A survey of the reactor status, and of the

actual contamination and exposure levels will be provided, together with a description of the

remediation activities and countermeasures adopted from the government institution, in the framework

of the international recommendations. Finally, the lesson learned from the Fukushima accident will be

discussed, and a short comparison with the Chernobyl experience will be attempted, to better understand

risks and consequences of a nuclear accident in the third millennium scenario. ________

Dottorato di Ricerca in Fisica dell’Università degli Studi di Messina 21 Novembre 2011, ore 15.00, Sala Seminari IPCF-CNR, V.le F. S. d‘Alcontres 37, S. Agata, Messina

Seminar title: Salty ice under pressure; Dr. Antonio Marco Saitta

Physique des Milieux Denses, IMPMC, CNRS-UMR 7590, Université Pierre et Marie Curie, Paris

Abstract Water, wherever it exists in nature, contains unavoidably significant amounts of dissolved ionic species.

Nonetheless, surprisingly little experimental attention has been paid on the high pressure behaviour of ―salt

water‖ compared to pure water. In a recent study combining neutron diffraction and molecular dynamics

simulations we showed the existence [3] of a polyamorphic transition in LiCl:6D2O between a high-density

(HDA) and a very-high-density amorphous (VHDA) form. In spite of the high amount of salt, LiCl:6D2O

vitrifies at ambient pressure in a structurally compact form very similar to the relaxed high-density

amorphous phase of pure water (e-HDA) [1]. We show that the transition to salty-VHDA takes place abruptly

at 120 K and 2 GPa under annealing at high pressure, is reversible. We suggest that the transition is linked to

a local structural reorganization of water molecules around the Li ions. The possible connection of this

transition with the analogous observed [1] in pure water and the generality of the occurrence of a

polyamorphism phenomenon in solutions in which one component, water, can have two critical points [2]

will be discussed. Under further annealing at high pressure (~4GPa), the salty-VHDA amorphous crystallizes,

for a temperature of ~270 K, in a new and unexpectedly simple salt hydrate [4], which can be regarded as an

―alloyed‖ high-pressure ice phase. Such ―salty‖ ice VII has significantly different structural properties

compared to pure ice VII, such as a 8% larger unit cell volume, 5 times larger displacement factors, frozen

rotational disorder, absence of transition to an ordered ice VIII structure, and most likely ionic conductivity.

Our study strongly suggests that there is a whole new class of salt hydrates based on various kinds of solutes

and high pressure ice forms. If these exist in nature in significant quantity, their physical properties would be

highly relevant for the understanding of icy bodies in the solar system.

[1] R. J. Nelmes et al., Nature Phys. 2 414, (2006).

[2] P. G. Debenedetti and H. E. Stanley, Phys. Today 40 (2003).

[3] L. E. Bove, S. Klotz, J. Philippe, and A. M. Saitta, Phys. Rev. Lett. 106, 125701 (2011).

[4] S. Klotz, L. E. Bove, T. Strassle, T. C. Hansen, and A. M. Saitta, Nature Materials 8, 405 (2009)


125

Dottorato di Ricerca in Fisica dell’Università degli Studi di Messina 1 Dicembre 2011, ore 15.00, Sala Seminari IPCF-CNR


Seminar title:

A novel hybrid top-down/bottom-up approach for nanoparticle synthesis:

Laser ablation in reversed micellar solution

Dr. Pietro Calandra IPCF-CNR Sede di Messina

If the building up of smaller and smaller structures promptly answers the recent technological request of

more and more miniaturized devices, it is also true that new and exotic features arise below a certain

size threshold of particles basically due to quantum confinement of charge carriers (Quantum Size

effects). In addition to size effects, further peculiar properties are expected to arise by controlling the

spatial location of different materials, e.g. semiconductor and metal domains, within each nanoparticle

[1]. In fact, it is well known that semiconductor/metal junctions give rise to very interesting phenomena

which have been exploited in a wide range of technological applications (transistors, rectificator

junctions, Ohmic contacts as well as effective photocatalysts).

In order to prepare A@B-type materials (A and B referring to two different materials), we set up a novel

synthetic method based on the laser ablation of a target of the material A, immersed in a reversed

micellar solution containing nanoparticles of the material B. This strategy is a winning example of an

hybrid approach combining, in a synergistic way, the advantages of a top-down approach (high purity of

the ablated particles [2]) and a bottom-up one (synthesis of B and self-assembly of A onto it).

[1] T. Hirakawa and P. V. Kamat, J. Am. Chem. Soc. 127, 3928 (2005).

[2] P. Calandra et al., Materials Letters 64, 576 (2010).

________

Dottorato di Ricerca in Fisica dell’Università degli Studi di Messina 5 Dicembre 2011, ore 15.00, Sala Seminari IPCF-CNR


Seminar title:

Magnetically induced birefringence in magnetic nanoparticles suspensions

Dr. Mikolaj Pochylski Division of Optics, Dept. of Physics, Adam Mickiewicz University, Poland

Abstract In this talk the magnetically induced birefringence method will be shown as a method useful in

discrimination between different mineral structures and sizes of magnetic nanoparticles. The basic

principles of the technique and its simple experimental realization will be explained. The applicability of

the method will be presented for several biomedically relevant systems.


126

Dottorato di Ricerca in Fisica dell’Università degli Studi di Messina 20 Dicembre 2011, ore 15.00, Aula E. Majorana, Dip.to di Fisica,


Seminar title:

La «particella di Dio» e l'origine della massa

Paolo Castorina Dipartimento di Fisica e Astronomia, Universita di Catania

Abstract

Al Centro Europeo Ricerche Nucleari (CERN) di Ginevra è in funzione la piùgrande macchina che

l'uomo abbia mai costruito: il Large Hadron Collider (LHC). Si accelerano e si fanno urtare particelle di

energia altissima perverificare le leggi fondamentali della Natura.

LHC ci ha già permesso di raggiungere temperature molto simili a quelle dell'inizio del Big Bang

cosmologico ed al CERN è stata anche intrappolata l'antimateria. Ma non siè ancora trovata la particella

di Higgs la cui esistenza confermerebbe completamente l'attuale teoria unificata delle interazioni

elettromagnetiche e deboli e, soprattutto, spiegherebbe l'origine della massa. La massa, anche quella

delle particelle più piccole, non è una proprietà fondamentale. Essa deriva dalle forze di interazione e, in

particolare, dall'esistenza di una nuova particella, battezzata "particella di Dio", attraverso un

affascinante meccanismo, detto rottura spontanea della simmetria, che viene descritto con semplici

esempi.

Infine, i recenti risultati preliminari di LHC, presentati al CERN il 12 Dicembre 2011 e riportati dalla

stampa internazionale, verranno brevemente discussi.


127

Organizzazione

del

Dottorato di Ricerca in Fisica dell‘Università di Messina

Ciclo (XXVI)


128

Organization and Personnel

PhD COORDINATOR : PROF. LORENZO TORRISI

TEACHERS OF REFEREMENT

FOR THE DIFFERENT CURRICULA:

PROF. G. CARINI CURRICULUM STRUTTURA DELLA MATERIA

PROF. GIORGIO GIARDINA CURRICULUM FISICA NUCLEARE

PROF. PAOLO V. GIAQUINTA CURRICULUM FISICA MAT. SOFF.

E DEI SIST. COMPL.

PROF. DOMENICO MAJOLINO CURRICULUM FISICA APPLICATA

DIRECTOR OF PHYSICS DEPARTMENT OF MESSINA

UNIVERSITY:

PROF. GIACOMO MAISANO

DIRECTOR OF MATTER PHYSICS AND ELECTRONIC

ENGINEERING DEPARTMENT:

PROF. FORTUNATO NERI

SCHOOL MANAGER: DR PAOLA DONATO

ADMINISTRATION PERSONNEL: Mrs. GIUSEPPA LA SPADA

Mrs. ROSANNA ARENA

Mrs. GAETANA PANTO’

Mr. SALVATORE RANDO


129

Curriculum di Struttura della Materia

(15 moduli/180 ore).

DISCIPLINA MODULI Prof.copertura

Fisica stati

condensati (45)

Fisica dello stato solido (15) Ginatempo

Fisica dei solidi amorfi (15) D‘Angelo

Fisica dei liquidi (15) Caccamo

Fisica Teorica (20) Fisica Relativistica (10) Savasta

Teoria dello scattering

elettromagnetico (10) Borghese

Metodi Matematici

e computazionali

della Fisica (30)

Tecniche di Calcolo della

Fisica (10) Savasta

Fondamenti di informatica e

Fisica computaz. (10) Costa-

Ginatempo

Simulazione di sistemi

all‘equilibrio (10) Costa-F.Sajia

Tecniche

Spettroscopiche

(40)

Spettr. Neutronica (10) Wanderlingh

Spettr. Ottica (10) Majolino

Spettr. Acustica e dielettrica

(10) Mandanici-

Tripodo

Spettr. Elettronica (10) Mondio

Fisica Sistemi

Complessi (30)

Fenomenologia dei sistemi

complessi (15) Magazù

Fisica sistemi a molti corpi

(15) Malescio-

Prestipino

Fisica Nucleare

(15) Teoria delle interazioni

fondamentali (15) Trifirò


130

Curriculum di Fisica della Materia Soffice e dei Sistemi complessi


DISCIPLINA MODULI

Prof.copertura

Fisica degli stati

condensati (45)

Fisica dei liquidi (15) Caccamo


Sistemi metastabili (15) Giaquinta

Fisica della Materia

soffice e dei sistemi

complessi (45)

Colloidi e polimeri e aggregati

supramolecolari (20)

Micali

Sistemi di interesse biofisico (15) Magazù

Sistemi caotici, finanziari; reti (10) Malescio

Argomenti avanzati di

Fisica dei Liquidi (20)

Miscele di liquidi e liquidi carichi

(10)

F. Saija

Liquidi a legame idrogeno (10) Mallamace

Tecniche

Spettroscopiche (30)



Spettr. Acustica e dielettrica (10) Mandanici-

Tripodo

Metodi Matematici e

computazionali della

Fisica (20)

Fondamenti di informatica e Fisica

computazionale (10)

Costa-

Ginatempo

Simulazione di sistemi

all‘equilibrio (10)

Costa-F.Saija

Metodi di

Simulazione Avanzati

(20)

Simulazione di sistemi fuori

dall‘equilibrio (10)

Prestipino

Metodi numerici per lo studio di

transizioni di fase (10)

Prestipino


131

Curriculum di Fisica Applicata ai Beni Culturali


DISCIPLINA MODULI Prof. copertura

Fisica stati condensati

(25)


Fisica dei Materiali (10) Mondio

Fisica Teorica (10) Teoria dello scattering

elettromagnetico (10)

Borghese-Iatì

Metodi Matematici e


Fisica (20)

Tecniche di Calcolo della Fisica

(10)

Savasta

Fondamenti di informatica e

Fisica computaz. (10)

Costa-Ginatempo

Tecniche


Introduzione alle tecniche

spettroscopiche (10)

Crupi



Spettroscopia Acustica e

dielettrica (10)

Mandanici-

Tripodo

Spettr. Elettronica (10) Mondio

Fisica dei sistemi

complessi (30)

Fenomenologia Sistemi complessi

(15)

Magazù

Fisica sistemi a molti corpi (15) Malescio-

Prestipino

Metodologie Fisiche

applicate ai Beni

Culturali (45)

Archeometria (10) Majolino

Metodologie Sperimentali e

strumentazione in Fisica applicata

ai Beni Culturali (15)

Torrisi-Magazù

Metodologie nucleari in Fisica

Applicata (20)

Barnà-Trifirò-

Fazio


132

Curriculum di Fisica Applicata ai Beni Ambientali



Fisica stati condensati

(30)

Fisica dello stato solido (15) Ginatempo


Fisica Teorica (10) Teoria dello scattering

elettromagnetico (10)

Borghese-Iatì

Metodi Matematici e


Fisica (20)

Tecniche di Calcolo della Fisica

(10)

Savasta

Fondamenti di informatica e Fisica

computaz. (10)

Costa-Ginatempo

Tecniche


Introduzione alle tecniche

spettroscopiche (10)

Crupi



Radioattività e Spettroscopia

Gamma (10)

Barnà - Trifirò

Fisica dei sistemi

complessi (30)

Fenomenologia Sistemi complessi

(15)

Magazù

Fisica sistemi a molti corpi (15) Malescio-

Prestipino

Metodologie Fisiche

applicate ai Beni

Ambientali (50)

Metodologie Sperimentali e

strumentazione in Fisica applicata

ai Beni Ambientali (15)

Torrisi-Magazù

Inquinamento Acustico e normativa

(15)

Federico

Metodologie nucleari in Fisica

Applicata (20)

Barnà-Trifirò-

Fazio


133

Curriculum di Fisica Nucleare



Fisica Teorica (10)

Teoria dello scattering elettromagn.

in processi Nucleari (10)

Iatì-Maidaniuk-

Giardina

Fisica Nucleare

(65)

Teoria delle interaz. Fondam. (15) Trifirò

Teoria delle reazioni Nucleari

indotte da ioni leggeri (10)

Giardina -

Nasirov

Teoria delle reazioni Nucleari

indotte da ioni pesanti (20)

Giardina -

Nasirov

Spettroscopia Nucleare (20) Barnà

Metodi Matematici

e computazionali

della Fisica (15)

Acquisizione ed elaborazione dei

dati sperimentali (15)

Barnà

Fisica Sistemi

Complessi (30)

Fenomenologia sistemi complessi

(15)

Magazù

Fisica dei sistemi a molti corpi (15) Malescio-

Prestipino

Apparati di

rivelazione in

Fisica Nucleare e

subnucleare (30)

Rivelazione dei prodotti di

reazione e metodologie di Analisi in

Fisica Nucleare (15)

Trifirò

Rivelazione dei prodotti di

reazione e metodologie di Analisi in

Fisica subnucleare (15)

Trifirò

Fisica subnucleare

(30)

Risonanze barioniche con sonde

elettromagnetiche in fisica

relativistica (10)

Di Salvo

Procedure di simulazione nelle

reazioni di fotoproduzione di

Mesoni (10)

Moricciani

Astrofisica Nucleare (10) Italiano


134

Collegio dei Docenti del

Dottorato di Ricerca in Fisica

Ciclo XXVI

1. Abramo Maria Concetta

2. Barnà Calogero Renato

3. Borghese Ferdinando

4. Branca Caterina

5. Caccamo Carlo

6. Carini Giuseppe

7. Costa Dino

8. Crupi Vincenza

9. Cutroni Maria

10. D‘Angelo Giovanna

11. Di Salvo Rachele Anna

12. Giaquinta Paolo Vittorio

13. Giardina Giorgio

14. Ginatempo Beniamino

15. Gucciardi Pietro

16. Iatì Maria Antonia

17. Magazù Salvatore

18. Maisano Giacomo

19. Majolino Domenico

20. Malescio Gianpietro

21. Mandanici Andrea

22. Maragò Onofrio

23. Micali Norberto

24. Mondio Guglielmo

25. Moricciani Dario

26. Prestipino Giarritta Santi

27. Saija Franz

28. Torrisi Lorenzo

29. Trifirò Antonio

30. Tripodo Gaspare

31. Wanderlingh Ulderico

[email protected];

[email protected];

[email protected];

[email protected];

[email protected];

[email protected];

[email protected];

[email protected];

[email protected];

[email protected];

[email protected];

[email protected];

[email protected];

[email protected];

[email protected];

[email protected];

[email protected];

[email protected];

[email protected];

[email protected];

[email protected];

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135

ELENCO DOTTORANDI DI RICERCA IN FISICA:

XXIV CICLO Curriculum

D‘ANDREA Cristiano Struttura della Materia [email protected]

FINA Natale Struttura della Materia [email protected]

RIFICI Simona Struttura della Materia [email protected]

SCARDINA Francesco Fisica Nucleare [email protected]

TRIMARCHI Antonio Struttura della Materia [email protected]

VILARDI Rocco Struttura della Materia [email protected]

XXV CICLO

CACCIOLA Adriano Struttura della Materia [email protected]

DI BARTOLO Federico Fisica Nucleare [email protected]

FISICHELLA Maria Fisica Nucleare [email protected]

MINNITI Triestino Fisica Nucleare [email protected]

ROMANIUK Mariia Fisica Nucleare [email protected]

SANTORO Simone Fisica Nucleare [email protected]

XXVI CICLO

CURCIARELLO Francesca Fisica Nucleare [email protected]

CUTRONEO Mariapompea Struttura della Materia [email protected]

DE LEO Veronica Fisica Nucleare [email protected]

SAYED Rania Strutt. della Materia [email protected]

STASSI Roberto Struttura della Materia [email protected]



















136

Tesi del Dottorato di Ricerca in Fisica

Ciclo XXIV

XXIV CICLO

DOTTORANDO CURRICULUM ARGOMENTO TESI TUTORE / CO-TUTORE

Dott. D‘Andrea

Cristiano Struttura della Materia Surface enhanced Raman spectroscopy di proteine

Dott. Pietro G.Gucciardi

Prof. Fortunato Neri

Dott. Fina

Natale Struttura della Materia

Nano-ottica: diffusione ed emissione di luce in

presenza di nanoparticelle metalliche.

Prof. Guglielmo Mondio

Dott. Salvatore Savasta

Dott.ssa Rifici

Simona Struttura della Materia

Struttura delle biomembrane investigata tramite la

spettroscopia NMR e la diffrazione di raggi X.

Prof. Ulderico

Wanderlingh

Dott. Scardina

Francesco Fisica Nucleare

Dynamics of the quark-gluon plasma in ultra-

relativistic heavy-ion collision. A transport theory

for the interaction between the minijets and the bulk

of the plasma.

Prof. Giorgio Giardina

Prof. Vincenzo Greco

Dott. Trimarchi

Antonio Struttura della Materia

Struttura e dinamica di biomembrane investigate

con small angle X-Ray scattering e spettroscopia di

neutroni.

Prof. Ulderico

Wanderlingh

Dott. Vilardi

Rocco Struttura della Materia

Interazione radiazione materia in regime non

perturbativo.

Prof. Ezio Bruno

Dott. Salvatore Savasta


137

Pubblicazioni 2011

degli studenti del Dottorato di

Ricerca in Fisica

dell’Università di Messina


138

PUBBLICAZIONI 2011 XXIV Ciclo

Cristiano D’Andrea

1. Re-Radiation Enhancement in polarized Surface-Enhanced Resonant Raman Scattering of Randomly Oriented

Molecules on Self-Organized Gold Nanowires, B. Fazio, C. D‘Andrea, F. Bonaccorso, A. Irrera, G. Calogero,

C. Vasi, P.G. Gucciardi, M. Allegrini, A. Toma, D. Chiappe, C. Martella, and F. Buatier de Mongeot, ACS

NANO, Vol 5, No 7 (2011) Pag. 5947-5956;

2. Manipulation and Raman Spectroscopy with Optically Trapped Metal Nanoparticles Obtained by Pulsed Laser

Ablation in Liquids, E. Messina, E. Cavallaro, A. Cacciola, R. Saija, F. Borghese, P. Denti, B. Fazio, C.

D‘Andrea, P. G. Gucciardi, M. A. Iati, M. Meneghetti, G. Compagnini, V. Amendola, and O.M. Maragò,

Journal of Physical Chemistry C 115 Issue 12 (2011) Pag. 5115-5122;

3. SERS activity of pulsed laser ablated silver thin films with controlled nanostructure E. Fazio, F. Neri, C.

D‘Andrea, P. M. Ossi, N. Santo and S. Trusso Journal of Raman Spectroscopy 42 (2011) Pag. 1298-1304;

4. Synthesis by pulsed laser ablation in Ar and SERS activity of silver thin films with controlled nanostructure, C.

D‘Andrea, F. Neri, P. M. Ossi, N. Santo and S. Trusso, Laser Physics 21 Issue 4 (2011) Pag 818-822.

5. Spectral dependence of the Amplification Factor in SERS (Poster), C. D‘Andrea, B. Fazio, A. Irrera, P. Artoni,

O.M. Maragò, M. A. Iatì, G. Calogero, P. G. Gucciardi, Proceedings International Summer School on

―Plasmonics, Functionalization and Biosensing‖, Kirchhoff Institute for Physics, University of Heidelberg, 24-

30 Aprile 2011;

6. Spectral dependence of the Amplification Factor in Surface Enhanced Raman Spectroscopy (Poster), C.

D‘Andrea, B. Fazio, A. Irrera, P. Artoni, O.M. Maragò, M. A. Iatì, G. Calogero, P. G. Gucciardi, Proceeedings

International Summer School on "NANO-OPTICS: Plasmonics, Photonic Crystals, Metamaterials and Sub-

Wavelength Resolution", Ettore Majorana Foundation and Centre for Scientific Culture, Erice (TP), 03-18

Luglio 2011;

7. Spectral dependence of the Amplification Factor in Surface Enhanced Raman Spectroscopy (Poster), C.

D‘Andrea, B. Fazio, A. Irrera, P. Artoni, O.M. Maragò, M. A. Iatì, G. Calogero, P. G. Gucciardi, Proceedinggs

Electromagnetic and Light Scattering XIII, Conference, Taormina 26-30 Settembre 2011.

Natale Fina

1. A.Ridolfo, N.Fina, O.Di Stefano, O.M. Maragò , S.Savasta. Photoluminescence from a Dimer Nanoantenna:

From Purcell Effect to Nanopolaritons. in Progress on ACS Nano.

Simona Rifici

1. S. Rifici, C. Crupi, G. D‘Angelo, G. Di Marco, G. Sabatino, V. Conti Nibali, A. Trimarchi and U.

Wanderlingh, “Effects of a short length alcohol on dimyristoylphosphatidylcholine system”, Philosophical

Magazine, 91 2014-2020, (2011);

2. S. Rifici, U. Wanderlingh, G. D‘Angelo, C. Crupi, A. Trimarchi, V. Conti Nibali, “Effects of medium-chain

alcohols on the structure of phospholipid bilayers”, Il Nuovo Cimento, in press.


139

Francesco Scardina

1. ―Impact of temperature dependence of the energy loss on jet quenching observables‖

F. Scardina, M. Di Toro, V. Greco. Oct 2011. 7 pp.

Published in Nuovo Cim. C34N2 (2011) 67-73

Antonio Trimarchi

1. S. Rifici, C. Crupi, G. D‘Angelo, G. Di Marco, G. Sabatino, V. Conti Nibali, A. Trimarchi and U.

Wanderlingh, ―Effects of a short length alcohol on dimyristoylphosphatidylcholine system‖, Philosophical

Magazine, 91 2014-2020, (2011);

2. S. Rifici, U. Wanderlingh, G. D‘Angelo, C. Crupi, A. Trimarchi, V. Conti Nibali, “Effects of medium-chain

alcohols on the structure of phospholipid bilayers”, Il Nuovo Cimento, IN PRESS;

3. U. Wanderlingh, G. D‘Angelo, V. Conti Nibali, A. Trimarchi, C. Crupi ―Anisotropic dynamics in phosholipid

membranes, a Fixed Energy Window neutron scattering study”, J. Chem. Phys. In press.

Rocco Vilardi

1. R. Vilardi, A. Ridolfo, S. Portolan, S. Savasta, O. Di Stefano, Quantum Complementarity of Cavity Photons

Coupled to a Three-Level System, to be published by Physical Review A;

2. Rocco Vilardi, articolo riguardante il trasferimento della coerenza, prossima pubblicazione su Le Scienze Web

News, ISSN 1827-8922;

3. Rocco Vilardi, articolo riguardante il progetto ELENA, prossima pubblicazione su Le Scienze Web News,

ISSN 1827-8922;

4. Rocco Vilardi, Alla ricerca del bosone di Higgs: nuova fisica al CERN?, Le Scienze Web News, 25 luglio

2011, ISSN 1827-8922;

5. Rocco Vilardi, Alessandro Ridolfo, Salvatore Savasta, Controllo ottico ultraveloce del dualismo onda

corpuscolo, Le Scienze Web News, 28 marzo 2011, ISSN 1827-8922;

6. A. Ridolfo, R. Vilardi, O. Di Stefano, S. Portolan, and S. Savasta, All Optical Switch of Vacuum Rabi

Oscillations: The Ultrafast Quantum Eraser, Physical Review Letters 106, 013601, January 05 2011;

7. Rocco Vilardi, Alessandro Ridolfo, Ultrafast Optical Control of vacuum Rabi Oscillations of a MicroCavity-

Single Quantum Emitter System, ACTIVITY REPORT 2010, pp.69-72, Lorenzo Torrisi Editore, Dottorato di

Ricerca in Fisica, Università degli Studi di Messina, c/o Dipartimento di Fisica, facoltà di Scienze-Università

di Messina, ISSN 2038-5889.


140

PUBBLICAZIONI 2011 XXV Ciclo

Adriano Cacciola

1. Manipulation and Raman Spectroscopy with Optically Trapped Metal Nanoparticles Obtained by Pulsed Laser

Ablation in Liquids, Messina E, Cavallaro E, Cacciola A, et al., JOURNAL OF PHYSICAL CHEMISTRY C

Volume: 115 Issue: 12 Pages: 5115-5122 Published: MAR 31 2011;

2. Plasmon-Enhanced Optical Trapping of Gold Nanoaggregates with Selected Optical Properties, Messina E,

Cavallaro E, Cacciola A, et al., ACS NANO Volume: 5 Issue: 2 Pages: 905-913 Published: FEB 2011;

3. Stratified dust grains in the interstellar medium. III Infrared cross-sections, Author(s): Iati M. A.; Cecchi-

Pestellini C.; Cacciola A.; et al., 12th International Conference on Electromagnetic and Light Scattering by

Nonspherical Particles - Theory, Measurements, and Applications, J. of Quantitative Spectroscopy & Radiative

Transfer, Volume: 112 Issue: 11 Special Issue: SI Pages: 1898-1906, 2011.

Federico Di Bartolo

1. L.Torrisi; L. Giuffrida, D. Margarone, F. Caridi, F. Di Bartolo, Low energy proton beams from laser-generated

plasma, NIM in Physics A, 653, 140T (2011);

2. L. Torrisi, F. Caridi, F. Di Bartolo, A. Baglione, M. Cutroneo, Ion Production and Detection from Laser-Thin

Targets Interaction, IEEE Transactions on Plasma Science, in press.;

3. F. Di Bartolo, F. Caridi, L. Torrisi, Mass Quadrupole Spectrometry applied to laser ion sources, Nucleonika.,

in press;

4. G. Castro, D. Mascali, F.P. Romano, L. Celona, S. Gammino, N. Gambino, D. Lanaia, R. Di Giugno, R.

Miracoli, T. Serafino, F. Di Bartolo and G. Ciavola, Comparison between off-resonance and Electron

Bernstein Waves heating regime in a Microwave Discharge Ion Source, Rev. Sc. Instr., (2011) in press.;

5. G. Castro, F. Di Bartolo, N. Gambino, D. Mascali, A. Anzalone, L. Celona, S. Gammino, R. Di Giugno, D.

Lanaia, R. Miracoli, F.P. Romano, T. Serafino, S.Tudisco, Ion acceleration in non-equilibrium plasmas driven

by fast drifting electron, Appl. Surf. Sc. (2011);

6. L. Torrisi, S. Cavallaro, S. Gammino, L. Andò, P. Cirrone, M. Cutroneo, R. Sayed, L. Giuffrida, F. Romano, F.

Caridi, F. Di Bartolo, A.M. Visco, A. Baglione, C. Scolaro, Proton generation from LIS at INFN-LNS

(LIANA project), INFN-LNS ACTIVITY REPORT 2010;

Maria Fisichella

1. Analysis of states in 13

C populated in 9Be +

4He resonant scattering

M. Freer, N. I. Ashwood, N. Curtis, A. Di Pietro, P. Figuera, M. Fisichella, L. Grassi, D. Jelavic Malenica,

Tz. Kokalova, M. Koncul, T. Mijatovic M. Milin, L. Prepolec, V. Scuderi, N. Skukan, N. Soic, S. Szilner, V.

Tokic D. Torresi, and C. Wheldon, Phys. Rev. C 84, 034317 (2011)

2. Fusion and direct reactions for the system 6He + 64Zn at and below the Coulomb barrier

V. Scuderi, A. Di Pietro, P. Figuera, M. Fisichella, F. Amorini, C. Angulo, G. Cardella, E. Casarejos, M.

Lattuada, M. Milin, A. Musumarra, M. Papa, M. G. Pellegriti, R. Raabe, F. Rizzo, N. Skukan, D. Torresi,

M. Zadr, Phys. Rev. C to be published

3. Li-α cluster states in 12B using 8Li + 4He inverse kinematics elastic scattering


141

D. Torresi, L. Cosentino, A. Di Pietro, C. Ducoin, P. Figuera, M. Fisichella, M. Lattuada, T. Lonnroth, C.

Maiolino, A. Musumarra, M. Papa, M.G. Pellegriti, M. Rovituso, D. Santonocito, G. Scalia, V. Scuderi and E.

Strano, M. Zadro, International Journal of Modern Physics E Vol. 20, No. 4 (2011) 1026–1029

4. Structure effects in the reactions 9,10,11

Be+64

Zn at the Coulomb barrier

V. Scuderi, A. Di Pietro, L. Acosta, F. Amorini, M.J.G. Borge, P. Figuera, M. Fisichella, L.M. Fraile,

J.Gomez-Camacho, H. Jeppesen, M. Lattuada, I. Martel, M. Milin, A. Musumarra, M. Papa, M.G. Pellegriti,

F. Perez-Bernal, R. Raabe, G. Randisi, F. Rizzo, D. Santonocito, G. Scalia, O. Tengblad, D. Torresi, A.M.

Vidal, M Zadro, Journal of Physics: Conference Series 267 (2011) 012012

5. Alpha structure of 12

B studied by elastic scattering of 8Li EXCYT beam on

4He thick target

M.G. Pellegriti, D. Torresi, L. Cosentino, A. Di Pietro, C. Ducoin, M. Lattuada, T. Lonnroth, P. Figuera, M.

Fisichella, C. Maiolino, A. Musumarra, M. Papa, M. Rovituso, V. Scuderi, G. Scalia, D. Santonocito, M.

Zadro, Journal of Physics: Conference Series 267 (2011) 012011

6. Halo effects on fusion cross section in 4,6

He+64

Zn collision around and below the coulomb barrier

M Fisichella, V Scuderi, A Di Pietro, P Figuera, M Lattuada, C Marchetta, M Milin, A Musumarra, M G

Pellegriti, N Skukan, E Strano, D Torresi, M Zadro, Journal of Physics: Conference Series 282 (2011) 012014

7. Structure effects and dynamics in fusion reactions of light weakly bound nuclei

E. Strano, A. DiPietro, P. Figuera, M. Fisichella, M. Lattuada, C. Maiolino, A. Musumarra, M G Pellegriti, D

Santonocito, V Scuderi, D Torresia, M Zadro, Journal of Physics: Conference Series 282 (2011) 012020

8. Fusion cross-section in the 4,6He + 64Zn collisions around the Coulomb barrier

M. Fisichella, Il Nuovo Cimento vol. 34C, 5 (2011)

Tino Minniti

1. T. Minniti and S. Santoro, ―Study of Nuclear equations of state:The ASY-EOS experiment at GSI‖

Activity Report 2010, Dottorato di Ricerca in Fisica, Università di Messina,. Torrisi Ed., 81-85, ISSN2038-

5889, 2011

Maria Romaniuk

1. M.V.Romaniuk, G.Giardina, G.Mandaglio, M.Manganaro, Meson Photoproduction and Baryon Resonances at

BGOOD , Activity report 2010 , Università di Messina, ISSN 2038-5889 (2010) 95-98;

2. V.S.Olkhovsky, M.V.Romaniuk, Non-relativistic-particle and photon two-dimensional above-barrier

penetration and sub-barrier tunneling through a barrier between initial and final free-motion regions along axis

normal to both planar interfaces, Journal of Modern Physics, 2011, 2, 1166-1171,

doi:10.4236/jmp.2011.210145. Published Online October 2011 G. Giardina, A. K. Nasirov, G. Mandaglio, F.

Curciarello,V. De Leo, G. Fazio, M. Manganaro, M. Romaniuk, C. Saccà, Investigation on the quasifission

process by theoretical analysis of experimental data of fissionlike reaction products, Journal of Physics:

Conference Series 282 (2011) 012006, doi:10.1088/1742-6596/282/1/012006;

Simone Santoro

1. I.Lombardo, L.Acosta, C.Agodi, F.Amorini, A.Anzalone, L.Auditore, I.Berceanu, G.Cardella, S.Cavallaro,

.B.Chatterjee, E.De Filippo, G.Giuliani, E.Geraci, L.Grassi, J.Han, E.La Guidara, G.Lanzalone, D.Loria,

C.Maiolino, T.Minniti, A.Pagano, M.Papa, S.Pirrone, G.Politi, F.Porto, F.Rizzo, P.Russotto, S.Santoro,

A.Trifirò, M.Trimarchi, G.Verde, M.Vigilante

“N/Z effects on evaporation residue emission near fragmentation treshold”

Proceeding of 14th

International Conference on Information Fusion, FUSION 2011, JUL 5-8 2011, Chicago

ILLINOIS USA - EPJ Web of Conferences 17 (2011) 16005


142

2. S. Santoro for CHIMERA and ASY-EOS Collaboration

“Study of nuclear equations of state: the ASY-EOS experiment at GSI”

Second International Symposium on Nuclear Symmetry Energy, NuSYM11, June 17-20 2011, at Smith

College in Northampton, Massachusetts, USA.

3. S.Santoro for ASY-EOS Collaboration

“Study of nuclear Equation Of State (EOS): the ASY-EOS experiment at GSI”

The Nuclear Chemistry Gordon Research Conference, June 12-17 2011 Colby-Sawyer College, New London,

New Hampshire, USA.

4. S.Santoro for ASY-EOS Collaboration

“ASY-EOS experiment at GSI: Chimera results”

ASYEOS collaboration meeting during the International Workshop on Multifragmentation and Related Topics

– 2011 at GANIL from 2nd

to 5th

November 2011, Caen, France.

5. G.Cardella, L.Acosta, C.Agodi, F.Amorini, A.Anzalone, L.Auditore, I.Berceanu, M.BChatterjiee, E.DeFilippo,

L.Grassi, E.La Guidara, G.Lanzalone, I.Lombardo, D.Loria, T.Minniti, A.Pagano, M.Papa, S.Pirrone, G.Politi,

F.Porto, F.Rizzo, E.Rosato, P.Russotto, S.Santoro, A.Trifirò, M. Trimarchi, G.Verde, M.Vigilante

“Reactions with exotic beams using the CHIMERA detector at LNS”

Conference on Structure and Dynamics of Nuclei far from Stability, September 15-16 2011, Dipartimento di

Fisica e Astronomia dell‘Università di Catania.

6. G.Cardella, L.Acosta, C.Agodi, F.Amorini, A.Anzalone, L.Auditore, I.Berceanu, M.BChatterjiee, E.DeFilippo,

L.Grassi, E.La Guidara, G.Lanzalone, I.Lombardo, D.Loria, T.Minniti, A.Pagano, M.Papa, S.Pirrone, G.Politi,

F.Porto, F.Rizzo, E.Rosato, P.Russotto, S.Santoro, A.Trifirò, M. Trimarchi, G.Verde, M.Vigilante

“Use of fragmentation beams at LNS with CHIMERA detector”

International Workshop on Multifragmentation and Related Topics – 2011 at GANIL from 2nd

to 5th

November

2011, Caen, France.

7. L. Acosta, T. Minniti, G. Cardella, G. Verde, F. Amorini, A. Anzalone, L. Auditore, M. Buscemi, A. Chbihi,

E. De Filippo, L. Francalanza, E. Geraci, C. Guazzoni, E. La Guidara, G. Lanzalone, I. Lombardo, S. Lo

Nigro, D. Loria, C. Maiolino, I. Martel, E.V. Pagano, A. Pagano, M. Papa, S. Pirrone, G. Politi, F. Porto, F.

Rizzo, P. Russotto, A.M. SánchezBenítez, J.A. Dueñas, R. Berjillos, S. Santoro, A. Trifirò, M. Trimachi, M.

Venhart, M. Veselsky, M. Vigilante

“FARCOS, a new array for femtoscopy and correlation spectroscopy”

International Workshop on Multifragmentation and Related Topics – 2011 at GANIL from 2nd

to 5th

November

2011, Caen, France.

8. S. Santoro per la collaborazione ASY-EOS

“Study of nuclear Equation Of State: the ASY-EOS experiment at GSI”

Società Italiana di Fisica – XCVII Congresso Nazionale, L‘Aquila, 26-30 Settembre 2011, p.35

9. Acosta L., Agodi C., Amorini F., Anzalone A., Auditore L., Bardelli L., Berceanu I., Cardella G., Chatterjee

M.B., De Filippo E., Grassi L., La Guidara E., Lanzalone G., Lombardo I., Loria D, Minniti T., Pagano A.,

Papa M., Pirrone S., Politi G., Porto F., Rizzo F., Russotto P., Santoro S., Trifirò A., Trimarchi M, Verde G.,

Vigilante M., “Misure con fasci di frammentazione ai LNS“


10. Acosta L., Amorini F., Anzalone A., Auditore L., Cardella G., Chbihi A., De Filippo E., Francalanza L.,

Geraci E., Guazzoni C., La Guidara E., Lanzalone G., Lombardo I., Lo Nigro S., Loria D., Martel I., Minniti

T., Pagano E.V., Pagano A., Papa M., Pirrone S., Politi G., Porto F.,Rizzo F.,Russotto P.,Santoro S., Trifirò A.,

Trimarchi M.,Verde G., Venhart M., Veselsky M., Vigilante M., “Il progetto FARCOS/EXOCHIM.”


11. Acosta L., Amorini F., Anzalone A., Auditore L., Cardella G., Chbihi A., De Filippo E., Francalanza L.,

Geraci E., Guazzoni C., La Guidara E., Lanzalone G., Lombardo I., Lo Nigro S., Loria D., Martel I., Minniti

T., Pagano E.V., Pagano A., Papa M., Pirrone S., Politi G.,Porto F., Rizzo F.,Russotto P.,Santoro S., Trifirò A.,

Trimarchi M., Verde G.,Venhart M., Veselsky M., Vigilante M.


143

“Dinamica e spettroscopia da studi di correlazioni con FARCOS/CHIMERA.”


12. F. Amorini, R. Bassini, C. Boiano, G. Cardella, E. De Filippo, L. Grassi, C. Guazzoni, Member, IEEE, P.

Guazzoni, M. Kiš, E. La Guidara, Y. Leifels, I. Lombardo, T. Minniti, A. Pagano, M. Papa, S. Pirrone, G.

Politi, F. Porto, F. Riccio, F. Rizzo, P. Russotto, S. Santoro, W. Trautmann, A. Trifirò, G. Verde, P. Zambon,

Student Member, IEEE, L. Zetta

“Light Charged Particle Identification by Means of Digital Pulse Shape Acquisition in the CHIMERA CsI(Tl)

Detectors at GSI Energies”, submitted paper on IEEE Transactions, to be published.

PUBBLICAZIONI 2011 XXVI Ciclo

Francesca Curciarello

1. G. Giardina, A. K. Nasirov, G. Mandaglio, F. Curciarello, V. De Leo, G. Fazio, M. Manganaro, M. Romaniuk,

C. Saccà: ―Investigation on the quasifission process by theoretical analysis of experimental data of fissionlike

reaction products‖, J. Phys.: Conf. Ser. 282, 012006 (1-20) (2011);

2. G. Fazio, G. Mandaglio, V. De Leo and F. Curciarello: “The Abrupt changes of the yellowed fibrils density on

the Linen of Turin”, Rad. Eff. and Def. in Solids, iFirst (2011);

3. O. Povoroznik, O. K. Gorpinich, O. O. Jachmenjov, H. V. Mokhnach, O. Ponkratenko, G. Mandaglio, F.

Curciarello, V. De Leo, G. Fazio and G. Giardina: ―High-lying 6Li levels at exicitation energy of around 21

Mev”, J. Phys. Soc. Jpn. 80 (2011) 094204.

Mariapompea Cutroneo

1. L. Torrisi, S. Cavallaro, M. Cutroneo, D. Margarone, S. Gammino

―Proton emission from a laser ion source‖

Participation to 14 th

ICIS 2011 Int. Conference, 12-16 Sept., Giardini Naxos (ME), Italy,

Accepted from Review of Scientific Instruments, 2011, in press.

2. D. Margarone, J. Krasa, J. Prokupek, A. Velyhan, L. Torrisi, A. Picciotto, L.Giuffrida, S.

Gammino, P. Cirrone, M. Cutroneo, F. Romano, E. Serra, A. Mangione, M. Rosinski, P.

Parys, L. Ryc, J. Limpouch, L. Laska, K. Jungwirth, J. Ullschmied, T. Mocek, G. Korn

and B. Rus

―New methods for high current fast ion beam production by laser-driven acceleration‖

Participation to 14 th


Accepted from Rev. Sci. Instr., 2011, in press.

3. L. Torrisi, S. Cavallaro, M. Cutroneo, L. Giuffrida, J. Krasa, D. Margarone, A. Velyhan,

J. Kravarik, J. Ullschmied, J. Wolowski, A. Szydlowski, M. Rosinski

―Monoenergetic proton emission from nuclear reaction induced by high intensity laser-

generated plasma‖, Participation to 14 th


Accepted from Review of Scientific Instruments, 2011, in press.

4. L. Torrisi, A. Italiano, E. Amato, F. Caridi, M. Cutroneo, C.A. Squeri, G. Squeri and A.M.

Roszkowska

―Radiation effects on poly(methyl methacrylate) induced by pulsed laser irradiations.

Radiation Effects & Defects in Solids 2011, in press.


144

5. M. Cutroneo, Relazione su invito alla Conferenza: ―X Giornata di Studio BIOINGEGNERIA - Facoltà di

Ingegneria Università di Catania - 1 luglio 2011‖ col lavoro: ―Fisica dei laser e loro interazione con la

materia‖, Proceeding 2011 in press.

6. Proceedings Conferenza 5th

PPLA (Plasma Production by Laser Ablation), Catania, 21-23 Set. 2011, col lavoro

―Laser ablation coupled to mass quadrupole spectrometer (LAMQS) and X-rays fluorescence for applications

in cultural heritage‖, in press.



―Proton emission from resonant laser absorption and self-focusing effects from hydrogenated structures”, in

press.



―XPS and XRF depth patina profiles of ancient silver coins‖, in press.

Veronica De Leo

1. G. Giardina, A.K. Nasirov, G. Mandaglio, F. Curciarello, V. De Leo, G. Fazio, M. Manganaro, M. Romaniuk,

C. Saccà, Investigation on the quasifission process by theoretical analysis of experimental data of fissionlike

reaction products, Journal of Physics: Conference Series 282 (2011) 012006;

2. O. Povoroznyck, O.K. Gorpinich, O. O. Jachmenjov, H.V. Mokhnach, O.Ponkratenko, G.Mandaglio,

F.Curciarello, V. De Leo, G. Fazio, and G. Giardina, ―High-Lying 6Li Levels at Exicitation energy of around

21 Mev‖, J. Phys. Soc. Jpn. 80 (2011) 094204;

3. G. Fazio, G. Mandaglio, V. De Leo and F. Curciarello: ―The Abrupt changes in the yellowed fibril density in

the Linen of Turin‖, Rad. Eff. and Def. in Solids, iFirst (2011).

Rania Sayed

1. M. G. Donato, P. G. Gucciardi, S. Vasi, M. Monaca, R. Sayed, G. Calogero, P.H. Jones, O.M. Maragò,

"Raman optical trapping of carbon nanotubes and graphene", Proceedings of CARBOMAT 2011, Catania, 5th-

7th December 2011;

2. Proceedings accepted for a poster presentation at CARBOMAT 2011, Workshop on Carbon-based

low-dimentional Materials, Catania, 5th-7th December, 2011.

Roberto Stassi

1. O. Di Stefano, R. Stassi, A. Ridolfo, S. Patané, and S. Savasta, Phys.Rev. B 84, 085324 (2011)


145

Foto

2a Giornata di Studio

del


dell‘Università di Messina

8 Novembre 2011,

Facoltà di Scienze M.M.F.F.N.N.

Biblioteca Centralizzata

V.le F. S. D‘Alcontres 31

S. Agata, Messina


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INDICE AUTORI

Artoni P pag. 89

Aversa M C 13

Cacciola D 21

Calogero G 61, 89

Caridi F 25, 55

Castro G 25

Celona L 25

Colonna M 101

Curciarello F 37, 65, 77

Cutroneo M 71

D‘Andrea C 61, 89

De Leo V 37, 65, 77

Di Bartolo F 25

Di Giugno R 25

Di Pietro A 31

Di Stefano O 85, 93

Di Toro M 101

Donato M G 81

Donato P 49

Fazio B 61, 89

Figuera P 31

Fina N 93

Fisichella M 31

Gammino S 25

Giaquinta P V 47

Giardina G 37, 65, 77

Greco V 101

Gucciardi P G 61, 81, 89

Irrera A 89

Lanaia D 25

Lattuada M 31

Magaudda D 15

Mandaglio G 37, 65, 77

Maragò O M 61, 81, 89, 93

Marchetta C 31

Mascali D 25

Micali N 61

Minniti T 33

Miracoli R 25

Musumarra A 31

Pellegriti M G 31

Ridolfo A 93

Rifici S 97

Romaniuk M 37, 65, 77

Ruiz C 31

Santoro S 41

Savasta S 85, 93, 109

Sayed R 81

Scardina F 101

Scuderi V 31

Shotter A 31

Stassi R 85

Strano E 31

Torresi D 31

Torrisi L 9, 25, 55, 71

Trimarchi A 105

Vilardi R 109

Villari V 61

Volpe G 81

Zadro M 31


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31 Dicembre 2011

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Facoltà di Scienze

Dipartimento di Fisica

Università di Messina

V.le F. Stagno D’Alcontres

S. Agata, Messina, Italy

Phone: +39 090 6765052

Fax: +39 090 395004

e-mail: Lorenzo. [email protected]

ISSN 2038-5889


Documents

ACTIVITY REPORT 2011 - unime.itww2.unime.it/dottoratofisica/ACTIVITY_REPORTS/Report PhD 2011.pdf · 1 issn2038-5889 dottorato di ricerca in fisica universitÀ di messina activity