MATRIX — 2005 › ~rfausto › matrix2005 › matrix_files › abstract_book.pdfMatrix –2005, The Physics and Chemistry of Matrix Isolated Species iii WELCOME The recent years

MATRIX — 2005

The Physics and Chemistry of Matrix Isolated Species

Funchal — Portugal

24-29 July 2005

SCIENTIFIC PROGRAMME

ABSTRACTS

LIST OF AUTHORS

Matrix – 2005, The Physics and Chemistry of Matrix Isolated Species

iii

WELCOME

The recent years have brought a substantial number of new developments and applications of matrix isolation spectroscopy. The chemical and physical nature of this expanding research field ranges from synthetic chemistry to solid-state physics. Laser vaporization in conjunction with low temperature matrix studies is one new technique whose introduction significantly facilitated the production and characterization of a great number of new radicals, ions and other transient species.

Today state-of-the-art studies combine spectroscopic investigations on mass selected atoms and molecules ("guests") with trapping in rare gas matrix ("host") environments. The mass-selection process, combined with the matrix trapping technique and spectroscopic detection, is a very powerful experimental approach, which allows to study a large number of new species. Other current challenge to chemical physics is a molecular level understanding of dynamics in condensed media. In this context, the study of the guest solvation and of guest-host interactions became an important problem. The small molecules in rare gas solids and their photodynamics represent ideal model systems for both experimental and theoretical studies of many-body interactions and dynamics. Although this field is young, it shows rapid progress due to (i) the widening accessibility of ultrafast lasers, which enable experiments on time scales of relevance to elementary processes in condensed matter and (ii) the accessibility of high-power computational tools, which permit large-scale simulations. Very interesting are also the matrix studies in novel and unusual matrices, such as the so-called "quantum hosts" like solid isotopes of hydrogen, and solid or liquid helium. The "quantum materials" exhibit large amplitude zero-point motion of their atoms or molecules and the importance of quantum effects in these matrices is greatly increased. Solid hydrogen is found to be a superior matrix for both high resolution vibration-rotation spectroscopy and the study of photochemical processes, a feature which is due to the extremely weak interactions in solid hydrogen. Further recent developments, which look extraordinarily promising, are the studies of helium clusters, the optical control of photochemical reactions through conformer selective ground state infrared excitation, spectroscopy of ionic species (including zwitterions) in ionic matrices, noble gas micro-matrices produced in expanding supersonic beams and spectroscopy in supercritical fluids.

Being held in Portugal for the first time, the biannual meeting of the Matrix Isolation Community will certainly be an excellent opportunity for spectroscopists, low temperature physicists and chemists, astrophysicists and surface chemists and physicists to present their research work to the international scientific community and discuss it with some of the most prestigious scientists in these fields of science. All the above-mentioned main topics and recent developments will be considered in MATRIX 2005. A special attention will be given to the progressively more important interplay between new experimental techniques and recently developed theories and computational methods. The scientific programme will put particular emphasis on phenomena, theories, experimental techniques and models that promise to be of interest for scientists in more than one field of research. Selected contributions and all abstracts presented in the congress will be published in a special volume of the JOURNAL OF MOLECULAR STRUCTURE.

As chairman of MATRIX 2005, I am now very pleased to extend a warm invitation to you to attend the congress and wish you a very nice stay in Funchal.

Rui Fausto, Ph.D


iv

THE ORGANIZING COMMITTEES OF THIS CONFERENCE GRATEFULLY ACKOWLEDGE THE FOLLOWING FOR THEIR CONTRIBUTION TO THE

SUCCESS OF THIS CONFERENCE

Faculdade de Ciências e Tecnologia Universidade de Coimbra

Universidade da Madeira

Fundação Luso-Americana para o Desenvolvimento

British Council

Fundação para a Ciência e a Tecnologia Secretaria Regional do Turismo e Cultura da Madeira

Fundação Calouste Gulbenkian Fundação Oriente

European Office of Aerospace Research and Development – Air Force Office of Scientific

Research – United Sates Air Force Research Laboratory

Presidência do Governo Regionalda Madeira

m. t. brandão, lda.

CRIOLABCold Fingers for Low Temperature Spectroscopy

criolab @ clix.pt Mobiliário de Laboratório


v

ORGANIZING COMMITTEES

International Scientific Committee

Chairman

Rui Fausto (Coimbra, Portugal)

Co-Chairs

Paula Castilho (Funchal, Portugal)

Werner Klotzbuecher (Muelheim an der Ruhr, Germany)

MembersSamuel Abrash (Richmond, USA)

Ara Apkarian (Irvine, USA)

Mario Fajardo (Edwards AFB, USA)

William Graham (Fort Worth, USA)

Murthy Gudipati (Moffett Field, USA)

Yan-Pern Lee (Hsinchu, Taiwan)

Zofia Mielke (Wroclaw, Poland)

Hideo Tomioka (Tsu, Japan)

Charles Wight (Salt Lake City, USA)

Organizing Committee

Rui Fausto (Coimbra)- Chairman

Paula Castilho (Funchal)- Vice-chair

Werner Klotzbuecher (Muelheim an der Ruhr)- Vice-chair

Ana Borba (Coimbra)

Susana Breda (Coimbra)

César Fernandes (Funchal)

Andrea Gómez-Zavaglia (Coimbra)

Susana Jarmelo (Coimbra)

Susy Lopes (Coimbra)

Ermelinda Maçôas (Coimbra)

Igor Reva (Coimbra)

João Rodrigues (Funchal)

The Organizing Committees of MATRIX 2005

Thank very much the lecturers and

participants by their valuable

contribution to the scientific programme

List of Lectures and Posters


xi

Main Plenary Lectures

PL 1- Matrix-Isolation: A Personal OverviewIan Dunkin

3

PL 2- Molecular Spectroscopy in Ice and Gas Phase in SpaceJosé Cernicharo

4

PL 3- Spectroscopy in Helium Nanodroplets: Quantum Physics and Exotic ChemistryRoger Miller

5

PL 4- Post-Hartree-Fock Density-Functional Correlation ModelsAxel Becke and Erin R. Johnson

6

PL 5- Relaxation Dynamics of Molecules in Quantum Crystal s Spectroscopy in Helium Nanodroplets: Quantum Physics and Exotic ChemistryTakamasa Momose

7

PL 6- Matrix Effects on Hydrogen-Bonded Molecular ComplexesAustin Barnes

8

PL 7- Photochemistry in Matrices - Recent ProgressMaciej Nowak

9

PL 8- Spectroscopy in Liquid Rare Gases: Recent AchievementsBenjamin van der Veken

10

PL 9- Laser Spectroscopy of Reactive Intermediates: C 2H2+

and C3-Rg ComplexesYen-Chu Hsu

11

PL 10- Rotational Isomerization in Rare-Gas Matrices Promoted bySelective Vibrational ExcitationLeonid Khriachtchev

12

PL 11- Infrared Spectra of Amino Acid Zwitterions Isolated in Alkali Halide MatricesGad Fischer

13

PL 12- Photochemical CO2 Splitting by H2O in Nanoporous Transition Metal SolidsHeinz Frei

14

PL 13- Matrix Isolation of Clusters in the Gas Phase - a Jet-FTIR StudyMartin Suhm

15


xii

Short Plenary Lectures

SL 1- Nuclear Spin Conversion of Water in Cryogenic MatricesX. Michaut, C. Parnadaut, A.-M. Vasserot and L. Abouaf-Marguin

19

SL 2- FTIR and DFT Studies of Carbon Chains and Metal -Carbon Species of Astrophysical Interest R. Cárdenas, S.A. Bates, E. Gonzalez, C.M.L. Rittby and W.R.M. Graham

20

SL 3- Modelling Matrix Environment Effect on Vibrational Energy Levels of Small Diatomics and Triatomics: Application to CO, NO, CO2 and O3P.R. Dahoo, A. Lakhlifi and J.M. Coanga

21

SL 4- Multinuclear NMR Spectroscopy in the Gas PhaseK. Jackowski

22

SL 5- Electronic Spectroscopy of Polycyclic Aromatic Hydrocarbons (PAHs) at Low Temperature in the Gas Phase and in Helium DropletsF.Huisken, A. Staicu, S. Krasnokutski, G. Rouillé and Th. Henning

23

SL 6- Librational States and Vibrational Spectrum of HA rF Molecule Trapped in Argon Matrix: Hybrid QM/DIM-Based ApproachA.V. Bochenkova and A.V. Nemukhin

24

SL 7- Intense-Field Alignment of Molecules Confined in Octahedral FieldsT. Kiljunen, B. Schmidt and N. Schwentner

25

SL 8- Infrared Spectroscopy of Hydrogen Bonding Systems in 1,4 -Butanediol Isolated in Low Temperature Ar and Xe MatricesM.T.S. Rosado, A.J.L Jesus, I.D. Reva, R. Fausto and J.S. Redinha

26

SL 9- The Structures of Some Small Clusters of Carbon Monoxide - An Infrared Matrix Isolation Spectroscopic and Ab Initio Molecular Orbital StudyL.M. Nxumalo, E.K. Ngidi and T.A. Ford

27

SL 10- Low Temperature Growth of Nanostructured Pb FilmV.E. Bochenkov and G.B. Sergeev

28

SL 11- Atomic Sodium Isolated in Rare-Gas Solids: A Comparison of Luminescence Apectroscopy and Molecular Dynamics CalculationsM. Ryan, P. dePujo, C. Crepin and J.G. McCaffrey

29

SL 12- Dynamics in Solid Parahydrogen Below 4 KD.T. Anderson

30

SL 13- Internal Rotation of CH3OH in Solid ParahydrogenY.-P. Lee and Y.-J- Wu

31

SL 14- Ultrafast IR-Driven Cis-Trans Isomerization of Nitrous AcidV. Botan, R. Schanz and P. Hamm

32


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SL 15- Acetylacetone Trapped in Inert Matrices: UV and IR Photo -Induced Isomerization and Theoretical Reactional PathwaysS. Coussan, A. Trivella, C. Manca, Y. Ferro, M. Rajzmann, R. Wieczorek, P. Piecuch, K. Kowalski, M. Wloch, S.A. Kucharski, M. Musial and P. Roubin

33

SL 16- The Photochemistry of Matrix Isolated Nitroso DerivativesJ. Glatthaar and A. Reichenberg

34

SL 17- Luminescence Spectroscopy of Matrix -Isolated Atomic Manganese -

Excitation of the "Forbidden" a6DJ l a

6S Transitions

M.A. Collier and J.G. McCaffrey

35

SL 18- Photochemistry of 5-Methyl-Coumalate: Matrix-Isolation FTIR and Theoretical StudyI.D. Reva, M.J. Nowak, L. Lapinski and R. Fausto

36

SL 19- Laser Spectroscopic Study of Mg Atoms in Pressurized Liquid He lium-3 and Helium-4Y. Moriwaki, F. Matsushima and N. Morita

37

SL 20- Semiclassical Correction for Tunnelling at Low TemperatureL.G. Arnaut

38

SL 21- Recent Adventures in d8 Transition Metal Halide ChemistryJohn F. Rooms, Adam J. Bridgeman, Ian R. Beattie, and Nigel A. Young

39

SL 22- ERS Study of H6+

and H4D2+

Produced in Irradiated Solid HydrogenT. Kumada, T. Takayanagi and J. Kumagai

40

SL 23- Spectroscopy and Application of Matrix Isolated One - and Bi-Photonic Reactions at 4-83 KG. Kaupp

41

SL 24- Matrix Isolation Spectroscopy on RDX Thermal Decomposition ProductsA. Pettersson, M. Norrefeldt, S. Wallin and H. Ostmark

42

SL 25- Novel Ketenimines and Nitrile Ylide Intermediates in Matrix Photochemistry of Carbenes and NitrenesC. Wentrup, P. Bednarek, L. George and D. Kvaskoff

43

SL 26- Matrix-Isolation and Computational Study of Phenylalanine Monomers

A. Kaczor, I. Reva, L. M. Proniewicz and R. Fausto

44

SL 27- The Preferred Conformers and Photochemical Reactivity ( O > 200 nm) of Serine and 3,3-Dideutero-Serine in the Neutral FormS. Jarmelo, L. Lapinski, M.J. Nowak, P.R. Carey and R. Fausto

45

SL 28- Thermal and Photoinduced Reactions in Mesogenic Cyanobiphenyl Matrices Doped by d- and f- Blok Metals at Low TemperatureT.I. Shabatina

46

SL 29- Environment Effects on the Vibrational Coherence of HCl : A Matrix Isolation StudyM. Broquier, C. Crépin, A. Cuisser, H. Dubost, J.-P. Galaup and B. Lebech

47


xiv

SL 30- Raman and NMR Spectroscopy on Matrix Isolated Sodium ClustersA. Kornath, S. Cappellacci, A. Kaufmann and R. Ludwig

48

SL 31- The Characterization of Molecular Alkali Metal AzidesJ.S. Ogden, J.M. Dyke, W. Levason, F. Ferrante and L. Gagliardi

49

Posters Session

1. History and Future of Matrix Isolation 53

P 1.1- 50 Years of Matrix Isolation SpectroscopyA. Kornath and L. Yovkova

55

2 - Matrix Isolation Spectroscopy in Astrophysics and Astrochemistry 57

P 2.1- Formation of the Insterstellar Molecules HNC 3 and HC3N from C3 and NH3J. Szczepanski, H. Wang, B. Doughty, J. Cole and M. Vala

59

P 2.2- VUV Irradiation of Urea Isolated in Cryogenic Matrix: Implications for Interstellar ChemistryF.Duvernay, T. Chiavassa, f. Borget and J.-P. Aycard

60

3 - Photochemistry in Matrices 61

P 3.1- Conformational Analysis and Photochemistry of Matrix -Isolated Propyl NitritesE. Mátyus, G. Magyarfalvi and G. Tarczay

63

P 3.2- Isomers of CNO2: Infrared Absorption of ONCO in Solid NeonY.-P- Lee, and Y.-J. Wu

64

P 3.3- FTIR Matrix-Isolation Spectroscopy and DFT Studies of Aliphatic Azide -Methyl Sulfides PhotochemistryM. Algarra, J.E. Rodriguez-Borges, M.N.D.S. Cordeiro, J. Mascetti, M. Lamotte, F. Borget, T. Chiavassa and J.P. Aycard

65

P 3.4- Conformational Properties of Trimethyl Phosphate MonomerA. Simão, I.D. Reva and R. Fausto

66

P 3.5- A Matrix Isolation Investigation of the Photochemical Products of the Oxidation of Benzene and its Derivatives with CrCl 2O2M.D. Hoops and B.S. Ault

67

P 3.6- A UV/Visible and Infrared Matrix Isolation Study of CrO 2Cl2 and OVCl3ComplexesN. Goldberg and B.S. Ault

68


xv

P 3.7- Matrix Effect on Triplet Luminescence of Self -Trapped Excitons in Rare-Gas CryocrystalsA.N. Ogurtsov, O.N. Bliznjuk, G. Stryganyuk, S. Vielhauer and G. Zimmerer

69

P 3.8- Photochemistry of Organic Radical Cations in SolidsM.Ya. Mel'nikov, V.I. Pergushov, E.A: Belokon and D.A. Tyurin

70

P 3.9- Stabilization of Radicals on Silica Surfaces: New Opportunities in the Investigation of the Mechanisms of Photochemical Reactions and Molecular Dynamics of RadicalsM.Ya. Mel'nikov and V.I. Pergushov

71

P 3.10- Molecular Structure, Vibrational Spectra and Photochemistry of 2-Methyl-2H-tetrazol-5-amine in Solid ArgonR. Fausto, I.D. Reva, L. Frija, M.L. Cristiano and A. Gómez-Zavaglia

72

P 3.11- Molecular Structure, Vibrational Spectra and Photochemistry of 5-Mercapto-1-methyltetrazole in Solid ArgonA. Gómez-Zavaglia, I.D. Reva, L. Frija, M.L. Cristiano and R. Fausto

73

P 3.12- Internal Rotation in Propionic Acid: Thermal and Photochemically Induced Processes and Tunneling in the Matrix Isolated MonomerE.M.S. Maçôas, L. Khriachtchev, M. Pettersson, R. Fausto and M. Räsänen

74

P 3.13- Conformational Flexibility, UV-Induced Decarbonylation and FT-IR Spectra of 1-Phenyl-1,2-Propanedione In Solid Xenon and in the Low Temperature Amorphous PhaseS. Lopes, A. Gómez-Zavaglia, L. Lapinski and R. Fausto

75

4 - Reactive Intermediates and Novel Species 77

P 4.1- Temperature Dependence of the Vergad-Kaplan BandsM. Norrefeldt, S. Andersson, S. Wallin and H. Ostmark

79

P 4.2- Does Hg(IV) Exist?J.F. Rooms, I.R. Beattie and N.A. Young

80

P 4.3- Search for Matrix-Isolated Cyanoacetylene-related IonsR. Kolos, M. Gronowski and P. Botschwina

81

P 4.4- On the Reactivity of Silicon and Germanium Atoms With Ethylene and PhosphaneJ. Glatthaar

82

P 4.5- Te2O4: Is it Cis or Trans?J.F. Rooms, C.J. Empson, A.J. Bridgemanand and N.A. Young

83

P 4.6- Organo-Noble-Gas Hydride Compounds HKrCCH, HXeCCH, HXeCC and HXeCCXeH: Formation Mechanisms and Effect of

13C Isotope Substitution on

the Vibrational PropertiesH. Tanskanen, L. Khriachtchev, J. Lundell and M. Räsänen

84


xvi

P 4.7- Infrared Absorption Spectrum of Matrix -Isolated Noble-Gas Hydride Molecules: Fingerprints of Specific Interactions and Hindere d RotationL. Khriachtchev, A. Lignell, J. Juselius, M. Räsänen and E. Savchenko

85

P 4.8- Tracking the Elusive "Os(CO)4"W.E. Klotzbücher

86

5 - Complexes, Clusters and Aggregates 87

P 5.1- Clustering of Orthohydrogen to N2O in Cryogenic Solid ParahydrogenB.D. Lorenz and D.T. Anderson

89

P 5.2- Thermo- and Photoinduced Silver Copper Nanosize Clusters Growth and Stabilization in Adamantane MatrizYu. N. Morozov, N. Sogoshi, V.A. Timoshenko, T.I. Shabatina and G.B. Sergeev

90

P 5.3- Low Temperature Paramagnetic Copper Atom Complexes with Mesogenic Alkylcyanobiphenyl LigandsA.A. Belyaev, A.A. Bogdanova, V.A. Timoshenko and T.I. Shabatina

91

P 5.4-Low Temperature Complexes of Samarium and Europium with Mesogenic Ligand 4-Penthyl-4'-Cyanobiphenyl and Their Solid State TransformationsT.I. Shabatina, A.V. Vlasov, A. Yu. Ivanov, G.G. Sheina and G.B. Sergeev

92

P 5.5- The Chemical Interactions of Silver Atoms and Nanosize Clusters with Carbon Tetrachloride in Mesogenic Cyanobiphenyl MatricesV.A.Timoshenko, T.I. Shabatina, A.A. Bogdanova, Yu.N. Morosov and G.B.Sergeev

93

P 5.6- Aggregation of Fluorinated AlcoholsT. Kalkowski, A Schutz, C. Emmeluth and M.A. Suhm

94

P 5.7- Matrix Isolation Vibrational Circular Dichroism Spectrum of 2 -Amino-1-PropanolG. Tarczay, E. Vass and G. Magyarfalvi

95

P 5.8- Lanthanide Aryloxides: Reactivity with POSST.A. Gasche, A.S. Correia, J. Branco, J. Carretas and A. Pires de Matos

96

P 5.9- Raman Spectroscopy on Arsenic and Antimony Clusters in Noble Gas MatricesA. Kornath, A. Kaufmann and S. Cappellacci

97

P 5.10- Pyrazole and Pyrrole Clusters in Slit Jet ExpansionsC.A. Rice, I. Dauster and M.A. Suhm

98

P 5.11- Computational and Spectroscopic Studies of Chiral Self -Recognition in Methyl Lactate ClustersTh. Adler, N. Borho, M.A. Suhm and M. Reiher

99

P 5.12- Non-adiabatic Dynamics of Electronically Excited Metal Clusters Embedded in an Ar MatrixJ. Douady, E. Giglio, B. Gervais, F. Fehrer, E. Suraud and P. G. Reinhard

100


xvii

P 5.13- DFT Modelisation of Spectroscopic Properties of Small Na Clusters Embedded in Rare Gas MatrixB. Gervais, E. Jacquet, E. Giglio, A. Ipatov, E. Suraud, P.G. Reinhard and J. Douady

101

P 5.14- Ethane Formation through the Sacrificial Hydrogenation of Ethene on Early Transition Metal AtomsM.G.K. Thompson and J. Mark Parnis

102

P 5.15- FTIR Spectroscopic Evidence for the Water Diethene Complex, C 2H4 ... HOH ... C2H4M.G.K. Thompson and J. Mark Parnis

103

P 5.16- Matrix Isolation and Ab Initio Study of the H 2O2…SO2 ComplexS. Pehkonen, J. Lundell, L. Khriachtchev, M. Pettersson and M. Räsänen

104

6 — General and Last Minute 105

P 6.1- Theoretical Investigation of the Reactivity of Cu and Cu 2 With OCS and CO2Y. Dobrogorskaya, J. Mascetti, I. Pápai and Y. Hannachi

107

P 6.2- Time Resolved CARS Measurements of I2 in Solid Kr: Vibrational State Dependent Dephasing Times Between 2.6 - 32 KT. Kiviniemi, J. Aumanen, P. Myllyperkio and M. Pettersson

108

P 6.3 - Consecutive Conformational Cooling (GG’→GT→GG) in Matrix-Isolated Dimethyl SulfiteA. Borba, A. Gómez-Zavaglia, P.N.N.L. Simões and R. Fausto

109

P 6.4- Matrix-isolation Infrared Spectroscopy of Vicinal ButanediolsA.J.L. Jesus, M.T.S. Rosado, I. Reva, R. Fausto and J.S. Redinha

110

P 6.5- Reactions of Single Crystals: A Study by Infrared and Raman MicrospectroscopyM.J. Almond, S.L. Jenkins, S.D.M. Atkinson and (the late) P. Hollins

111

P 6.6- Modelling Reflexion Absorption Infrared Polarized Spectroscopy of Matrix Trapped Diatomics and TriatomicsJ.M. Coanga, E. Davy-Loutete, A. Lakhlifi and P.R. Dahoo

112

P 6.7- Low Temperature Vibrational Spectra of Diazines in Condensed State and Isolated in Argon MatricesS. Breda, I. Reva, L. Lapinski and R. Fausto

113

P 6.8- Photoinduced Electron Transfers in Supercritical Medium. A New Look at the Marcus Inverted Region.P. Gomes, C. Serpa, L. Arnaut, S. Formosinho, J. Seixas de Melo and J. Pina

114

P 6.9- Crystal Field Splitting of a6D State Atomic Manganese in Kr MatricesO. Byrne, M. Collier, C. Murray, M. Ryan and J. G. McCaffrey

115

Plenary Lectures


- 3 -

PL 1

Matrix Isolation: A Personal Overview

Ian Dunkin

Department of Chemistry, University of Strathclyde, 295 Cathedral Street, G1 1XL Glasgow, UK

A short history of the applications of the matrix-isolation technique, particularly in organic chemistry, will be given. Emphasis will be placed on the central role that IR spectroscopy has played in the study of reactive species, and the lecture will include examples of successes and pitfalls. Finally, the recent development of density functional theory as a reliable computational technique for predicting IR spectra of matrix isolated species will be discussed, again with examples.


- 4 -

PL 2

Molecular Spectroscopy in Ices and Gas Phase in Space

José Cernicharo

Departamento de Astrofisica Molecular e Infrarroja - Instituto de Estructura de la Materia - CSIC, C/Serrano 121 - 28006 Madrid - Spain

[email protected]

I am going to review the results obtained in the last years in mid and far-IR astrophysics concerning the observation of molecules and ices in interstellar and circumstellar environments (ISO, SIRTF). The spectroscopic capacities of future space missions such as Herschel will be presented and the science that could be done with this space platform will be discussed. The connection between Astrophysics and Laboratory Molecular Physics will be analyzed.


- 5 -

PL 3

Spectroscopic Studies in Helium Nanodroplets: Quantum Physics and Exotic Chemistry

Roger E. Miller

Department of Chemistry, University of North Carolina, Chapel Hill, N.C. 27599

[email protected]

Helium nanodroplets have immerged as an novel medium for forming and spectroscopically characterizing a wide range of clusters and nanoscale materials. Infrared laser spectroscopy has proven to be particularly powerful, given that the resolution in the associated spectra is often very high. In fact, the spectra of solvated molecules and clusters often show well resolved rotational (and sometimes hyperfine) structure that can be used to either probe the nature of the interactions between the dopant and the helium solvent or to probe the structure of the clusters formed in the droplets. The number of atoms and/or molecules doped into the droplets can be varied at will, by passing the droplets through a chamber maintained at an appropriate partial pressure of the species of interest.

Free radical clusters are being formed in helium nanodroplets and studied using high resolution infrared laser spectroscopy. The radicals of interest are formed by pyrolyzing a suitable precursor molecule, using a high temperature source. We currently have sources for I, Br, Cl, F and a range of organic radicals. Other approaches are being developed for N and O atoms and OH and CN radicals. Pick-up of the radicals is accomplished by passing the helium droplet beam close to the exit from the source. Complexes containing metals, semiconductors, salts and biomolecules have also been formed and spectroscopically invenstigated. In several cases, we clearly show that the rapid cooling of the growing species in the helium results in the stabilization of highly metastable species that would be difficult or impossible to form using more conventional, gas phase approaches.


- 6 -

PL 4

Post-Hartree-Fock Density-Functional Correlation Models

Axel D. Becke and Erin R. Johnson

Department of Chemistry, Queen’s University, Kingston ON K7L 3N6 Canada

[email protected]

In recent years, we have developed density functionals for correlation to be partnered with exact exchange (Kohn-Sham or Hartree-Fock). We have succeeded in designing functionals for all types of correlation encountered in chemistry: nondynamical, dynamical, and dispersion. Particular attention will be given to the last of these in this presentation. A simple and economical new model for computing intermolecular and intramolecular dispersion energies will be fully described.


- 7 -

PL 5

Relaxation Dynamics of Molecules in Quantum Crystals

Takamasa Momose

CREST, JST, and Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, JAPAN

Department of Chemsitry, Department of Physics and Astronomy, The University ofBritish Columbia, 2036 Main Mall, Vancouver, B.C. V6T 1Z1, CANADA

[email protected]

Solid hydrogen, known as a quantum crystal, is the simplest and most fundamental molecular crystal. Each hydrogen molecule in the crystal exhibits almost free rovibrational motion retaining the rotational quantum number J as a good quantum number. It has been shown that optical transitions to such quantized rotation-vibration states show extremely sharp linewidths [1]. For example, the first overtone Q2(0) [v = 2 ← 0, J = 0 ← 0] transition of solid parahydrogen appeared at 8070 cm-1 shows the linewidth as narrow as 0.0005 cm-1 (= 15 MHz) as shown in Figure 1 [2]. The sharp linewidthes were also observed for molecules embedded in solid parahydrogen [3]. The lineshape and width of such narrow transitions gives us rich information on relaxation dynamics of excited states.

Here, we discuss relaxation dynamics of vibrational excited states of molecules in solid parahydrogen. Detailed studies of temperature dependence of linewidths revealed that the pure dephasing is a dominant relaxation mechanism at very low temperatures [5,6]. However, there is a clear discrepancy between the theory and experiment on the temperature dependence of the dephasing. In addition, there is certainly some contribution of pure dephasing even at the limit of 0 K. We analyze the observed data by a first principle calculation to interpret the observed relaxation behaviour.

8070.5808070.5758070.5708070.5658070.5608070.555cm

-1

Figure 1 – First overtone Q2(0) [v = 2← 0, J = 0← 0] transition of solid parahydrogen

[1] T. Oka, Annu. Rev. Phys. Chem. 44, 299 (1993). [2] H. Katsuki, T. Nakamura, and T. Momose, J. Chem. Phys. 116, 8881 (2002). [3] T. Momose, H. Hoshina, M. Fushitani, and H. Katsuki, Vib. Spectrosco, 34, 95 (2004). [4] H. Katsuki, M. Fushitani, and T. Momose, Low Temp. Phys. 29, 832 (2003). [Fiz. Nizk. Temp. 29, 1093 (2003).] [5] H. Katsuki and T. Momose, Phys. Rev. Lett. 84, 3286 (2000). [6] D. Ando, Y. Miyamoto and T. Momose, in preparation.


- 8 -

PL 6

Matrix Effects on Hydrogen-bonded Molecular Complexes

Austin J. Barnes

Institute for Materials Research, University of Salford, Salford M5 4WT, Great Britain

[email protected]

The various models historically proposed to interpret solvent effects on the vibrational spectra of molecules will be briefly reviewed to demonstrate the inadequacy of dielectric continuum models and the importance of so-called specific interactions. Solvent effects on the position of conformational equilibria and hydrogen bonding/proton transfer equilibria will also be covered [1]. Examples will be drawn from both solution spectra in traditional solvents at ambient temperature and cryogenic noble gas solutions. The implications for the interpretation of matrix spectra will be discussed along with the additional phenomena that result from the rigid matrix environment.

There has recently been a resurgence of interest in matrix effects on the degree of proton transfer in strongly hydrogen-bonded acid-base molecular complexes, marked by the publication of new matrix isolation data by Andrews et al. for the prototypical ammonia – hydrogen chloride complex [2] and also for ammonia – hydrogen bromide and ammonia – hydrogen iodide [3], and a considerable number of theoretical studies of environmental effects on amine – hydrogen halide and other strongly hydrogen-bonded complexes. The gas phase and matrix isolation data for amine – hydrogen halide complexes are re-examined in the light of the new experimental data and theoretical interpretations to provide a detailed analysis of matrix effects on the extent of proton transfer in this important series of complexes [4]. Generalisation of this analysis to other strongly hydrogen-bonded molecular complexes will be attempted in order to interpret the more fragmentary data available for complexes such as ammonia – nitric acid and the amine – carboxylic acid complexes.

[1] C. Reichardt, Solvents and Solvent Effects in Organic Chemistry, 2nd edition, VCH, Weinheim (1988). [2] L. Andrews, X. Wang, Z. Mielke, J. Am. Chem. Soc., 123 (2001) 1499; J. Phys. Chem. A, 105 (2001) 6054. [3] L. Andrews, X. Wang, J. Phys. Chem. A, 105 (2001) 6420; 7541.[4] A.J. Barnes, Z. Latajka and M. Biczysko, J. Mol. Struct., 614 (2002) 11.


- 9 -

PL 7

Photochemistry in Matrices - Recent Progress

Maciej J. Nowak

Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw, Al. Lotnikow 32/46, [email protected]

Recent results concerning photoinduced unimolecular isomerization processes in low-temperature matrices will be reported in this lecture. During last two years, the new examples of the intramolecular proton transfer photoreactions of the type:

N

R1

R2H

X

N

R1

R2

XH

hQ

X = O, S, Se

,have been observed: (i) the reaction was found in simple thioamides (thioacetamide, thiourea); (ii) photoinduced tautomerizations involving multiple proton transfer were observed in 2,4-dithiouracil (double proton transfer) or trithiocyanuric acid (triple proton transfer); (iii) the first proofs of the photoreversibility of such reactions have been obtained for thiouracils, e.g.:

N

N

CH3

H

S

O

N

N

CH3

S

H

O

hQ

The competitive photoreactions occur in D-pyrones, azinones and diazinones:(i) photogeneration of Dewar valence isomers

O

R2

O

R1

R3 O

R2

O

R1

R3N

N

O

R1

R2 R3

N

N

OR1

R3

R2

hQhQ

(ii) ring opening reactions:

NY

X

H

OY

X

ON

H

N

N

R

O

N

ON

R

OO

R1

R2

R3O

R1

R2

R3O

hQ hQ hQX, Y = C, C

C, N

1 � � &

Domination of one of these types of photoisomerisation over the other depends on the kind of heteroatom(s) and its/their position in the ring. Conjugative type substitution at the ring promotes generation of Dewar isomers and hinders ring-opening processes.

Photoisomerizations in N4-hydroxycytosines:

N

N

N

O

R2

R1

R3

O

R

N

N

N

O

R2

R1

R3

O

R

syn anti

hQ

The final stage of these photoprocesses is the photostationary state, which depends on substituent(s) and on the applied wavelength of UV light used for irradiation. The recent theoretical calculations showed the existence of conical intersection between the ground and excited states of hydroxycytosine. This intersection appears at the geometry with imino =NOH group oriented perpendicularly to the plane of the ring. This result provides a new interpretation of the mechanism of syn - anti isomerization.


- 10 -

PL 8

Spectroscopy in Liquid Rare Gases: Recent Achievements

Benjamin. J. van der Veken

Department of Chemistry, University of Antwerp, Groenenborgerlaan 171, B2020 Antwerp Belgium

[email protected]

The talk will highlight some of the work that we have been doing over the last few years in the field of vibrational spectroscopy using liquid rare gases as solvents. Two topics will be treated, one on van der Waals complexes, and the other on some “special effects”.

Recently we have studied the complex formed in liquid argon between dimethyl ether and carbon dioxide [1]. In the infrared spectra, very weak transitions of the complex were observed in the region of the symmetric stretch of carbon dioxide, that were assigned as the well-known Fermi doublet. It will be discussed that the observed frequencies, however, are disturbed not only by a Fermi resonance, but most likely also by a Darling-Dennison resonance.

Cryosolutions can be used to determine stabilities of weak complexes, as will be exemplified by the benzene/hexafluorobenzene supramolecular synthon [2].

Liquid rare gases such as argon and krypton are very well suited for the study of weak interactions formed with C-H bonds. In a number of cases these weak hydrogen bonds induce a blue shift of the stretching frequency of the C-H bond [3,4]. Here we will show how Raman spectroscopy helps in the identification of such blue shifts [5]. Also, the influence of a Fermi resonance in fluoroform on the observed blue shifts will be discussed [6], and we will demonstrate that for haloform complexes with dimethyl ether, oxirane and acetone the correlation of the blue shift with the complexation enthalpy of the complex is low [7]. For the second topic, we will first show how infrared spectroscopy in liquid argon doped with some krypton or xenon, has helped to explain the presence of a Q branch in the infrared spectrum of the stretching mode of dissolved hydrogen chloride [8]. Further, we present an interpretationof the sharp, weak transitions that are observed superposed on the induced absorption bands of oxygen and nitrogen in solutions in liquid argon and krypton and in liquid oxygen/nitrogen mixtures [9].

Cryosolution spectroscopy is not limited to the use of argon, krypton or xenon as solvents, as will be demonstrated by the infrared spectra of hydrogen deuteride, HD, dissolved in liquid neon [10].

Finally, liquid rare gases are ideally suited to study the effects of resonant dipole interactions. Already for dilute solutions, with mole fraction of a solute in liquid argon as low as 0.001, effect of binary solute/solute interactions can be observed, and we will illustrate how these effects can be simulated by a relatively simple model [11].

[1] P. Van Ginderen, W.A. Herrebout, B.J. van der Veken, Journal of Physical Chemistry A 107 (2003) 5391. [2] W. Vanspeybrouck, W.A. Herrebout, B.J. van der Veken, J. Lundell, R.N. Perutz, J. Phys. Chem. B 107 (2003) 13855. [3] S.N. Delanoye, W.A. Herrebout, B.J. van der Veken, Journal of the American Chemical Society 124 (2002) 11854.[4] S.N. Delanoye, W.A. Herrebout, B.J. van der Veken, Journal of the American Chemical Society 124 (2002) 7490.[5] T. Van den Kerkhof, A. Bouwen, E. Goovaerts, W.A. Herrebout, B.J. van der Veken, Physical Chemistry Chemical Physics 6 (2004) 358. [6] W.A. Herrebout, S.M. Melikova, S.N. Delanoye, K.S. Rutkowski, D.N. Shchepkin, B.J. Van der Veken, Journal of Physical Chemistry A in print (2005).[7] S.N. Delanoye, W.A. Herrebout, B.J. Van der Veken, Journal of Physical Chemistry A submitted (2005). [8] A. Medina, J.M.M. Roco, A. Calvo Hernandez, S. Velasco, M.O. Bulanin, W.A. Herrebout, B.J. van der Veken, Journal of Chemical Physics 116 (2002) 5058.[9] W. Herrebout, B. Van der Veken, M.O. Bulanin, A.P. Kouzov, to be published (2005).[10] W. Herrebout, B. Van der Veken, A.P. Kouzov, M.O. Bulanin, Physical Review Letters 92 (2004) 023002.[11] T.D. Kolomiitsova, D.N. Shchepkin, K.G. Tokhadze, W.A. Herrebout, B.J. van der Veken, Journal of Chemical Physics 121 (2004) 1504.


- 11 -

PL 9

Laser Spectroscopy of Reactive Intermediates:

C2H2+ and C3-Rg Complexes

Yen-Chu Hsu

Institute of Atomic and Molecular Sciences, Academia Sinica, P. O. Box 23-166, Taipei 106, Taiwan

[email protected]

It has been shown that the electronic transitions involving large geometry changes are particularly useful to observe some long vibrational progressions. The vibronic levels

(X4=0-6, X5=0-2, K=0-3) of the trans- and cis-bending vibration of C2H2+ ( X

~) and the

vibrational levels of the in-plane and out-of-plane bending vibration of the C3-Rg ( X~

) (Rg= rare gas atom) complexes have been determined by us from the electronic spectra recorded under a supersonic molecular beam condition. The two-color pulsed-field-induced zero-kinetic photoelectron spectroscopic technique was applied to study the ro-

vibronic levels of C2H2+ ( X

~), where several ro-vibrational levels of the tran-bent

uA 31~

state were chosen as the intermediate levels. Not only levels of pure Q4 vibration,

levels of pure Q5 and combination excitations were also observed. From the fit of 43 observed vibronic levels, the signs and values of the Renner parameters of these two normal modes were determined and the obtained spectroscopic parameters indicated that these two normal modes are interacting through the Darling-Dennison resonance.

In the studies of the C3-Rg ( X~

) complexes, the ground electronic states of the complexes were probed by the comet system of C3 by the laser-induced fluorescence (LIF). From the emission spectra, the C3-bending vibrational levels of the C3-Rg complexes were obtained. As the C3-bending amplitude increases in each complex, the vibrational energy was found to be progressively shifted to the lower values by comparing with those of free C3. The red (energy) shift also increases with the polarizability of the rare gas atom. A perturbed harmonic oscillator model [1] fits well the observed C3-bending manifolds of the C3-Ar, C3-Kr, and C3-Xe van der Waals complexes; therein the dipole-induced dipole interaction is primarily responsible for our observations. And the observed levels of the C3-Ar, C3-Kr, and C3-Xe complexes were tentatively assigned as (X2, X4)=(1, Xb-1), where Xb= X2+ X4. In the C3-Ne complex, it is much complicated; more than one vibrational level was observed in each Xb-manifold. The LIF spectral intensities obtained at several molecular beam temperatures suggest that the electronic excited state of the C3-Ne complex could have more than two conformations. Despite the complications, the binding energies of each complex versus the C3 bending motion follow a good trend with the X2 dependence of the dipole moment of C3 calculated by Jensen [2].

[1] G. Zhang, B.-G. Lin, S.-M. Wen, and Y.-C. Hsu, J. Chem. Phys. 120 (2004) 3189.[2] Per Jensen, private communication.

Source of funding: Academaia Sinica and National Science of Council, Taiwan, R. O. C.


- 12 -

PL 10

Rotational Isomerization in Rare-Gas Matrixes Promoted by Selective Vibrational Excitation

Leonid Khriachtchev

Laboratory of Physical Chemistry, P.O. Box 55, FIN-00014 University of Helsinki, Finland

[email protected]

The rotational isomerization (rotamerization) of matrix-isolated molecules can be efficiently produced by their vibrational excitation. The matrix-site selectivity of the light-induced rotamerization process was first demonstrated for HONO and (FCO)2 [1,2]. This observation shows that the rotamerization process is promoted by the direct vibrational excitation of the molecule, and non-resonant energy flow in the matrix is of minor importance. It follows that the rotamerization upon narrow-band tunable excitation can be a tool of reactive vibrational excitation spectroscopy [3-5].

The experiments with selective vibrational excitation provide data aiding the identification of various molecular conformers as it was demonstrated for oxalic (HOOCCOOH), malonic (HOOCCH2COOH), and maleic (HOOCCH=CHCOOH) acids [3,4,6]. By optical pumping of the ground-state trans conformers, the higher-energy cis forms of formic (HCOOH), acetic (CH3COOH), and propionic (CH3CH2COOH) acids were prepared [7-9]. The trans to cis conversion can be achieved even if the pumping energy is somewhat below the predicted reaction barrier, and a tunneling mechanism was suggested for this effect [10].

For formic, acetic, and propionic acids, the higher energy cis conformer decays back to the ground state trans conformer via a tunneling mechanism, and the cis to transtunneling rates of these species show remarkable host and temperature dependencies [11-13]. The quantum yields of IR-induced rotational isomerization were measured for these species in various rare-gas matrixes [5,12,13]. The comparison of the results obtained for these three acids develops the understanding of mechanisms involved in intramolecular vibrational energy redistribution in the solid phase, however, a number of observations have no interpretation yet.

[1] L. Khriachtchev et al., J. Chem. Phys., 113 (2000) 4265. [2] S. Sander et al., J. Mol. Spectrosc., 203 (2000) 145. [3] E. M. S. Maçôas et al., J. Phys. Chem. A, 104 (2000) 6956. [4] E. M. S. Maçôas et al., J. Phys. Chem. A, 104 (2000) 11725. [5] E. M. S. Maçôas et al., J. Chem. Phys., 119 (2003) 11765. [6] E. M. S. Maçôas et al., J. Phys. Chem. A, 105 (2001) 3922. [7] M. Pettersson et al., J. Am. Chem. Soc., 119 (1997) 11715. [8] E. M. S. Maçôas et al., J. Am. Chem. Soc., 125 (2003) 16188. [9] E. M. S. Maçôas et al., J. Phys. Chem. A (to be published). [10] M. Pettersson et al., J. Am. Chem. Soc., 125 (2003) 4058. [11] M. Pettersson et al., J. Chem. Phys., 117 (2002) 9095. [12] E. M. S. Maçôas et al., J. Chem. Phys., 121 (2004) 1331. [13] E. M. S. Maçôas et al., Phys. Chem. Chem. Phys., 7 (2005) 743.


- 13 -

PL 11

Infrared Spectra of Amino Acid Zwitterions Isolated

in Alkali Halide Matrices

Gad Fischer

Department of Chemistry, The Australian National UniversityCanberra, ACT 0200, Australia

[email protected]

Much research endeavour is devoted to elucidation of molecular structures and to understanding of the intramolecular interactions. Vibrational spectroscopy provides an excellent vehicle to undertake such studies. The approaches are varied. Vapour phase spectroscopy is useful for thermally stable volatile substances, generally small molecules, where large signals can be generated but may be complicated by rotational band contours and the presence of hot bands. On the other hand spectroscopy in supersonic molecular beams or in low temperature inert gas matrices overcomes temperature induced problems but may be inappropriate for other reasons. In standard laboratory techniques most infrared absorption spectra of solid substances are recorded in the form of microcrystals in alkali halide, generally KBr, pressed pellets or as microcrystals in paraffin mulls. Where intermolecular interactions are strong the vibrational data obtained may be a poor representation of the isolated molecule.

Many hydrocarbon molecules containing heteroatoms are characterized by strong intra and intermolecular hydrogen bonds. In the infrared spectra these interactions are reflected by the appearance of broad and poorly structured absorption contours extending over many hundreds of cm-1 in the region of the CH stretching modes, and by broadened and multiple bands in lower frequency regions. As a consequence the information that can be gained from analysis of the vibrational spectra is limited. This is particularly pertinent for the amino acids and peptides, the building blocks of proteins, since in polar solutions and in the crystal they exist as zwitterions stabilized by strong intermolecular interactions. In low temperature inert gas matrices the zwitterions revert to the un-ionized molecules. It has been found that the low dielectric constants of the alkali halides are sufficient to stabilize the zwitterions and to allow study of the vibrational spectra in the absence of strong intermolecular interactions.

A novel technique has been developed to prepare samples of the amino acids and related molecules isolated in alkali halide matrices. The technique involves the deposition of a fine spray of an aqueous solution that is both very dilute in the sample but saturated in the alkali halide, on to an infrared transparent disk. It has been shown that this method prepares the sample molecules largely as monomolecular zwitterions isolated in room-temperature ionic matrices. The method is significantly different to a standard evaporation to dryness approach where microcrystals are formed. Computational studies based on the Onsager dipole sphere model which is appropriate to the nature of the samples, are useful in predicting molecular structures and spectra.


- 14 -

PL 12

Photochemical CO2 Splitting by H2O in Nanoporous

Transition Metal Solids

Heinz Frei

Physical Biosciences Division, Calvin Laboratory, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720

[email protected]

The photoreduction of CO2 by H2O is one of the key chemical reactions for the generation of a renewable fuel like methanol using sunlight as energy source. Robust inorganic photoreactors offer an attractive approach, but progress has been hampered by the lack of materials with catalytic sites that accomplish the conversion under visible instead of short wavelength ultraviolet light. Metal-to-metal charge-transfer (MMCT) transitions of oxo-bridged binuclear units anchored on the large inner surfaces of nanoporous silica matrices offer robust sites for visible light-induced CO2 activation.

A method has been developed for assembling completely inorganic binuclear moieties consisting of a CO2-activating center like Ti or Zr and a donor such as Cu

I or SnII

on the pore surface of MCM-41 silica sieve [1,2]. TiOCuI, TiOSnII, or ZrOCuI groups anchored on the silica pore surfaces exhibit MMCT absorptions (e.g. TiIV-O-CuI Æ TiIII-O-CuII) extending into the visible or near infrared region. The groups were structurally characterized by optical, FT-IR, FT-Raman, and XANES spectroscopy. Observation of the Cu-O (or Sn-O) bond modes allowed us to directly demonstrate covalent anchoring on the pore surface and monitor oxidation state changes during photoredox reactions. Irradiation of the MMCT chromophore of ZrCuI-MCM-41 sieve loaded with 1 atm of CO2gas at room temperature resulted in the splitting to CO and surface OH radicals. This is the first observation of CO2 photoreduction at a binuclear MMCT site, and forms the basis for the exploration of a photochemical Z-scheme for the reduction of CO2 by H2O to a C-based liquid fuel.

Parallel mechanistic studies of CO2 reduction by H2O in Ti framework substituted mesoporous silica matrices under UV light will be presented as well [3]. Static and time-resolved step-scan FT-IR spectroscopy revealed that ligand-to-metal charge-transfer excitation of the framework TiO sites results in the conversion of CO2 by H2O to CO and O2 by a single photon.

[1] W. Lin and H. Frei. Photochemical CO2 Splitting by Metal-to-Metal Charge-Transfer Excitation in Mesoporous ZrCu(I)-MCM-41 Silicate Sieve. J. Am. Chem. Soc. 2005, 129, 1610. [2] W. Lin and H. Frei. Anchored Metal-to-Metal Charge-Transfer Chromophores in Mesoporous Silicate Sieve for Visible Light Activation of Ti Centers. J. Phys. Chem. B 2005, 109, 000. [3] W. Lin, H. Han, and H. Frei. CO2 Splitting by H2O to CO and O2 under UV Light in TiMCM-41 Silicate Sieve. J. Phys. Chem. B 2004, 108, 18269.

This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, Division of Chemical, Geological, and Biosciences of the U.S. Department of Energy under contract No. DE-AC03-76SF00098


- 15 -

PL 13

Matrix Isolation of Clusters in the Gas Phase - A Jet-FTIR Study

Martin A. Suhm

Institut fur Physikalische Chemie, Tammannstr. 6, Universitaet Goettingen, 37077 Goettingen, Germany

[email protected]

Matrix isolation spectroscopy has been providing a wealth of structural and dynamical information on molecular clusters since many decades. Due to its sensitivity, matrix isolation allows for cluster characterization via universal infrared absorption techniques. The comparison to quantum-chemical predictions is sometimes complicated by matrix induced spectral shifts and site splittings. These matrix effects are not easily calculated [1] for molecular clusters. Typically, free and matrix isolated clusters are not jointly investigated by experiment, either.

We present a sensitive supersonic jet technique [2] by which the infrared spectra of molecular clusters can be studied in a wide range of states, spanning isolated non-equilibrium clusters and equilibrated clusters which are coated by a more or less amorphous matrix. In between, various states of thermal relaxation and matrix embedding can be probed. Thus, the technique offers information on matrix shifts, conformational states, and isomerizations in molecular clusters in a single experimental setup.

Applications of the technique include HCl [2], water [3], methanol [3], carboxylic acids [3], alpha-hydroxyesters [4], pyrazole [5], and ethanol [6]. The talk will focus on the most recent applications to clusters of aliphatic alcohols and their fluorinated derivatives, where a subtle interplay between conformation and hydrogen bond topology is observed.

[1] A. V. Bochenkova, M. A. Suhm, A. A. Granovsky, A. V. Nemukhin, J. Chem. Phys., 120 (2004) 3732-3743; [2] T. Häber, U. Schmitt and M. A. Suhm, Phys. Chem. Chem. Phys. 1 (1999) 5573-5582; [3] T. Häber, U. Schmitt, C. Emmeluth, M.A. Suhm, Faraday Discussions 118 (2001) 331-359, 53, 119, 174-175, 179-180, 304-309, 361-363, 367-370; [4] N. Borho, M. A. Suhm, Phys. Chem. Chem. Phys. 6 (2004) 2885-2890; [5] C. A. Rice, N. Borho, M. A. Suhm, Z. Phys. Chem. 219 (2005) 379-388; [6] C. Emmeluth, V. Dyczmons, T. Kinzel, P. Botschwina, M. A. Suhm, M. Yáñez, Phys. Chem. Chem. Phys. 7 (2005) 991-997

Short Lectures


- 19 -

SL 1

Nuclear Spin Conversion of Water in Cryogenic Matrices

Xavier Michaut, Cédric Pardanaud, Anne-Marie Vasserot,

and Luce Abouaf-Marguin

Laboratoire de Physique Moléculaire pour l'Atmosphère et l'Astrophysique, Université Pierre et Marie Curie - 4 place Jussieu – 75252 Paris

[email protected]

Water, like other hydrogenated molecules of astrophysical interest H2, NH2, or H2CO, exists in two nuclear spin configurations. The molecule is called ortho if the spins of the protons are parallel (total nuclear spin I=1) or para if the spins are anti-parallel (total nuclear spin I=0). In the gas phase, each rotational state is associated with only one nuclear spin species. In the high temperature limit (T>50 K), 3/4 of the molecules are ortho while 1/4 are para. Below 50 K, the ortho to para ratio becomes strongly temperature dependent. From the analysis of infrared emission spectra of cometary comae [1-3], or absorption of dark clouds [4], some ortho to para populations ratio can be measured. It is supposed to be determined by the formation conditions of molecules in space, and more specifically by the formation temperature. In this context, we have undertaken a study of some parameters involved in the nuclear spin conversion of water trapped in rare gas matrices at low temperatures.

We present here a study, in the mid-infrared, of H2O in neon, argon, and krypton matrices between 6 and 45 K. The spectra were recorded in the frequency range 400-4000 cm-1 with resolutions of 0.15 and 0.03 cm-1 using a Bruker 113V FTIR spectrometer. In the vibrational Q1, Q2 and Q3 regions of water, the spectrum exhibits severalrovibrational lines weakly shifted from the corresponding gas phase ones. Besides these lines, at 6 K in the Q2 bending mode, a wide structure is attributed to the coupling of the rotation with the translation (RTC) of the molecule within the cage [5]. After a fast cooling from 30 K to 6 K, the populations of ortho and para species are first frozen in a nonequilibrated distribution, before slowly reach the Bolztmann equilibrium. Following the time evolution of the intensities of the rovibrational transitions, we were able to measure characteristic times of nuclear spin conversion in different conditions. At 6 K, a typical time of 70 minutes in neon matrix (mole ratio 1/1000) is reduced to 35 minutes by double-doping the sample with a paramagnetic species like O2. In argon matrix [5], the nuclear spin conversion with O2 is twice slower than in neon and is strongly accelerated at 30 K. Recent calculations performed by our group show that the average distance between molecules isolated in the matrix is a predominent parameter for O2-enhanced nuclear spin conversion. However, the physical reasons (interactions with phonons, size of the cage, long distance interactions,…) of the differences observed in our experiments are not completely identified yet and it is surprising that characteristic times in cryogenic matrices are much shorter than the duration of months estimated in ice by Tikhonov and Volkov [6] or billions of years expected in comets [1-3].

[1] J. Crovisier, Faraday Discuss. ,109 (1998) 437. [2] H. Kawakita, J.-I. Watanabe, R. Furusho, T. Fuse, M. T. Capria, M. C. De Sanctis, and G. Cremonese, Astrophys. J., 601 (2004) 1152. [3] N. Dello Russo, B. P. Bonev, M. A. DiSAnti, M. J. Mumma, E. L. Gibb, K. Magee-Sauer, R. J. Barber, and J. Tennyson, Astrophys. J., 621 (2005) 537. [4] J. E. Dickens, and W. M. Irvine, Astrophys. J. , 518 (1999) 733. [5] X. Michaut, A.-M. Vasserot, and L. Abouaf-Marguin, Vib. Spectrosc., 34 (2004) 83. [6] V. I. Tikhonov, and A. A. Volkov, Science, 296 (2002) 2363.


- 20 -

SL 2

FTIR and DFT Studies of Carbon Chains and Metal-Carbon Species of Astrophysical Interest

R. Cárdenas, S.A. Bates, E. Gonzalez, C.M.L. Rittby and W.R.M. Graham

Department of Physics and Astronomy, Texas Christian University, Fort Worth, Texas 76129

[email protected]

Mono-metal carbon clusters are likely to be present in the circumstellar shells of stars and perhaps, in interstellar space. The envelope expelled by the prototypical carbon star IRC +10216, is known to be rich both in metal-bearing molecules such as NaCl, KCl, AlCl, AlF, NaCN, MgNC, and MgCN [1] and in carbon chains such as C5, C5H, C6H, and SiC4 [2]. No molecules containing the transition metal elements Fe, Ni, Cr, and Mn, which are highly abundant in cosmic space, have yet been detected in stellar atmospheres orinterstellar space, but this is probably because of the lack of laboratory data, since transition metals are very likely to have reacted with the carbon chains present.

Pure carbon chains and metal-carbon chains and clusters formed by trapping the products of Nd-YAG laser ablation in solid Ar at ~10 K are being investigated. FTIR measurements of vibrational frequencies and 13C isotopic shifts coupled with the results of DFT-B3LYP calculations are being used to determine geometric structures and identify vibrational fundamentals. Species to be discussed include the C10 and C11 carbon chains and mono-metal carbon chains formed with Cr, V, and Ti metals.

[1] E. Yamazaki, T Okabayashi, and M. Tanimoto, Astrophys. J., 55 (2001) L199 and references therein. [2] P.R. Bernath, K.H. Hinkle, and J.J. Keady, Science, 244 (1989) 562.

Work supported by the Welch Foundation and TCU Research and Creative Activities Fund.


- 21 -

SL 3

Modelling Matrix Environment Effect on Vibrational Energy Levels of Small Diatomics and Triatomics: Application to CO, NO CO2 and O3

P. R. Dahoo, A. Lakhlifi and J. M. Coanga

Laboratory of Magnetism and Optics of Versailles,UMR 8634, 45 Av des Etats Unis, 78 035 Versailles Cedex

Department of Physics, University of Versailles St Quentin en Yvelines, 45 Av des Etats Unis, 78 035 Versailles Cedex

Laboratoire d’Astrophysique de l’Observatoire de Besançon, UMR 6091, 41 bis avenue de l'Observatoire,BP 1615, Université Franche-Comté, 25010 Besançon, France

[email protected]

In Rare Gas (RG) matrices, it is observed that vibrational frequencies of diatomics and triatomics occur at lower frequencies than those observed in gas phase. The shifts are relatively small, typically less than 0.5% of the observed frequencies. Force constant values derived from matrix data then differ only slightly from gas phase ones.The shifts can thus be determined by small perturbation treatment of the quadratic terms in the intramolecular potential energy of the trapped molecule [1, 2]. A theoretical model is applied to calculate the shifts by combining methods commonly used in solid state physics to determine the distortion of an ideal lattice by a trapped molecule, that is use of the green function technique, with those regularly used to study gas phase theoretical spectroscopy, that is use of contact transformation as perturbation technique for vibrational energy levels calculations. Vibrational energies for low-lying levels of two diatomics CO, NO and two triatomics CO2 and O3 have thus been calculated up to 3000 cm-1. Results are compared from the point of view of the trapping site effect, the shifts observed for the different fundamental vibrational modes and the effect of the phonon –vibron coupling on the relaxation constants of intramolecular energy levels. Results calculated with CO2 are compared with experimental results ones [3] on laser induced fluorescence of CO2 in RG.

[1] P. R. Dahoo, I.Berrodier, V.Raducu, J.L. Teffo, H. Chabbi, A. Lakhlifi and L. Abouaf-Marguin, Eur. Phys. J. D. 5, (1999) 71. [2] P. R. Dahoo, A. Lakhlifi and H. Chabbi, J.Chem.Phys. 111 (1999) 10192. [3] H. Chabbi, B. Gauthier-Roy, A.-M. Vasserot, and L. Abouaf-Marguin J.Chem.Phys. 117 (2002) 4436.


- 22 -

SL 4

Multinuclear NMR Spectroscopy in the Gas Phase

Karol Jackowski

Laboratory of NMR Spectroscopy, Department of Chemistry, University of Warsaw, ul. Pasteura 1, 02-093 Warszawa, Poland.

[email protected]

Modern NMR spectroscopy can be successfully used for the analysis of gaseous mixtures and for investigations of numerous medium-size molecules in gaseous matrices. It extends the application of NMR spectroscopy as the analytical tool for investigations in the gas phase. NMR spectral parameters, like nuclear magnetic shielding or spin-spin coupling constants, are modified by intermolecular interactions when they are measured for any macroscopic sample. The standard values free from intermolecular interactions can be determined only in the gas phase when the parameters are investigated in a wide range of solvent density and extrapolated to the zero-density limit. With the use of gaseous matrices (Xe and SF6) we have observed multinuclear NMR spectra of 13C and 15N-enriched acetonitrile [1,2], 13C-enriched benzene [3], 13C-enriched iodomethane [4], 17O-enriched water [5] and many other compounds. It has been shown that all NMR spectral parameters are more or less density-dependent in the gas phase. It obviously means that only the parameters extrapolated to the zero-density point well represent the data of isolated molecules and can be compared with the ab initio calculations of magnetic shielding and spin-spin coupling. It is also shown that our accurate measurements in gaseous matrices enable us to obtain new values of nuclear magnetic moments for 13C, 15N, 17O, 19F and 33S [6]. It is demonstrated that only these new values provide consistent data for NMR absolute shielding constants for all the considered nuclei.

[1] M. Wilczek, W. Kozminski, K. Jackowski, Chem. Phys. Lett. 358 (2002) 263. [2] K. Jackowski, M. Wilczek, J. Mol. Struct. 651 (2003) 259. [3] K. Jackowski, E. Maciaga, M. Wilczek, J. Mol. Struct. (2005) in press. [4] M. Wilczek, M. Kubiszewski, K. Jackowski, J. Mol. Struct. 704 (2004) 311. [5] A. Antusek, K. Jackowski, M. Jaszunski, to be published.


- 23 -

SL 5

Electronic Spectroscopy of Polycyclic Aromatic Hydrocarbons (PAHs) at Low Temperature in the Gas Phase

and in Helium Droplets

F. Huisken, A. Staicu, S. Krasnokutski, G. Rouillé, and Th. Henning

Max Planck Institute for Astronomy, D-69117 Heidelberg

University of Jena, D-07743 Jena, Germany

[email protected]

Neutral and cationic polycyclic aromatic hydrocarbons (PAHs) are discussed as possible carriers of the diffuse interstellar bands (DIBs), still unassigned astrophysical absorption features observed in the spectra of reddened stars [1]. Despite the importance of this class of molecules for astrophysics and nanophysics (PAHs can be regarded as nanoscale fragments of a sheet of graphite), the spectroscopic characterization of PAHs under well-defined conditions (low temperature and collision-free environment) has remained a challenge.

Recently we have set up a cavity ring-down spectrometer combined with a pulsed supersonic jet expansion to study neutral and cationic PAHs under astrophysical conditions. PAH molecules studied so far include anthracene [2] and pyrene [3]. Employing another molecular beam apparatus, the same molecules were also studied in liquid helium droplets [3,4]. This novel technique combines several advantages of conventional matrix spectroscopy with those of gas phase spectroscopy. Notable advantages are the possibility to study molecules with low vapor pressure and to use a mass spectrometer facilitating spectral assignments.

The most recent studies were devoted to phenanthrene and the more complicated (2,3)-benzofluorene. These molecules were investigated in the gas phase by cavity ring-down spectroscopy and in liquid helium droplets using depletion spectroscopy. For benzofluorene the present studies constitute the first reported measurements both in the gas phase and in helium droplets. The origin of the S1 m S0 gas phase transition could be located at 29 894.3 cm-1, and a series of vibronic bands was recorded below 31 500 cm-1. In contrast to previously studied PAHs, the shift induced by the helium droplets was very small (blue shift between 4.5 and 4.9 cm-1 for all vibronic bands). With this new gas phase data, a value of 247 cm-1 is derived for the red shift experienced by the molecule in an argon matrix [5].

[1] F. Salama et al., Astrophys. J. 526 (1999) 265. [2] A. Staicu, G. Rouillé, O. Sukhorukov, Th. Henning, and F. Huisken, Molec. Phys. 102 (2004) 1777. [3] G. Rouillé et al, J. Chem. Phys. 120 (2004) 6028. [4] S. Krasnokutski, G. Rouillé, and F. Huisken, Chem. Phys. Lett. in press. [5] J.Banisaukas, J. Szczepanski, M. Vala, and S. Hirata, J. Chem. Phys. A 108 (2004) 3713.

This work was supported by the Deutsche Forschungsgemeinschaft (DFG).


- 24 -

SL 6

Librational States and Vibrational Spectrum of HArF Molecule Trapped in Argon Matrix: Hybrid QM/DIM-based Approach

A. V. Bochenkova and A.V. Nemukhin

Department of Chemistry, Moscow State University, Leninskie Gory, 119992 Moscow, Russia

[email protected]

Vibrational spectra and various trapping site structures of HArF in solid argon, recently discovered in low temperature matrices and characterized by infrared absorption spectroscopy [1], are studied by using the original hybrid diatomic-in-molecules (DIM) –based QM/MM approach. In the frame of the QM/DIM method the HArF molecule is treated at the MP2/6-311++G(2d,2p) level, while the guest-host interactions are described in terms of the reduced non-empirical DIM scheme based on the proper mixing between neutral and ionic states of the system [2].

A detailed analysis of the resulting QM/DIM potential energy (hyper-)surface (PES) reveals three types of the microscopic structure of the trapping sites within the C4v, C2v, and C3v local symmetries, representing thermally unstable and two stable configurations, respectively. The calculated differences in harmonic frequencies of the H-Ar stretching and H-Ar-F bending vibrations between these sites are in quantitative agreement with the experimental data obtained before and after annealing [3]. The experimental fine splitting of the bands in the H-Ar stretching region is attributed to the certain morphology of the matrix sites, paying attention to the specific positions of vicinal vacancies with respect to the trapped molecule [4]. Molecular dynamics simulation on the QM/DIM potential energy surface was carried out to investigate the local behaviour of impurities in the argon matrix.

The possible influence of the hindered rotation of the embedded molecule in the lattice on the infrared absorption spectrum is analysed. Librational eigenvalues and states of HArF inside the matrix are calculated by solving the rotational Scrödinger equation in the external potential of the equilibrated static and flexible argon surrounding. The rotational PES imposes the high barriers with respect to the rotational constant of the molecule, leading to the librational limit of the rotational problem. The obtained level structure and low-energy transitions are tentatively traced to the blue-shifted broad spectral feature in the H-Ar stretching region for the thermally unstable configuration.

[1] L. Khriachtchev, M. Pettersson, R. Runeberg, L. Lundell, and M. Räsänen, Nature (London), 406 (2000) 874. [2] A.V. Bochenkova, D.A. Firsov, and A.V. Nemukhin, Chem. Phys. Lett, 405 (2005) 165. [3] L. Khriachtchev, M. Pettersson, A. Lignell, and M. Räsänen, J. Am. Chem. Soc., 123 (2001) 8610. [4] L. Khriachtchev, A. Lignell, and M. Räsänen, J. Chem. Phys., 120 (2004) 3353.


- 25 -

SL 7

Intense–Field Alignment of Molecules Confined

in Octahedral Fields

Toni Kiljunen a, Burkhard Schmidt b and Nikolaus Schwentner a

a Institut für Experimentalphysik, FU-Berlin, Arnimallee 14, 14195 Berlin, Germanyb Institut für Mathematik II, FU-Berlin, Arnimallee 2-6, 14195 Berlin, Germany

[email protected]

The concept of molecular alignment by nonresonant laser fields is extended into solid phase [1].

We investigate the combined effect of a static octahedral potential and an anisotropic interaction with intense, linearly polarized laser pulses on the rotational motion of linear molecules. Time-independent computations reveal a rich pattern of avoided crossings of energy levels corresponding to pendular states with different degree of alignment along the laser field polarization. Time-dependent computations put forward a scheme to manipulate the alignment by adiabatic and nonadiabatic passages through the avoided crossing regions, thus allowing for (i) control over direction-dependent reaction mechanisms in solids [2] and (ii) analysis of crystal field splittings, respectively.

Figure 1 – Distribution of the rotational density is defined by the matrix potential shape and interaction strengthN. Panel a) shows a correlation from the free rotor energy spectrum to a librator and inserted the resulting six preferred orientations as rotational density lobes in a Cartesian reference frame. Panel b) depicts the energy levels in the presence of a laser field forN ��, and the squeezing of the ground state density along the field direction at'Z = 50 ('Z = 10-11 'D[Å3] I[W cm-2] / B[cm-1]).

[1] T. Kiljunen, B. Schmidt and N. Schwentner, Phys.Rev.Lett., (2005) accepted. [2] T. Kiljunen, M. Bargheer, M. Gühr, N. Schwentner and B. Schmidt, PCCP, 6 (2004) 2932.

Funding: Academy of Finland and Deutsche Forschungsgemeinschaft through program Sfb 450.


- 26 -

SL 8

Infrared Spectroscopy of Hydrogen Bonding Systems in 1,4-Butanediol Isolated in Low Temperature Ar and Xe Matrices

Mário T. S. Rosado, António J. L. Jesus, Igor D. Reva,

Rui Fausto and José S. Redinha

Department of Chemistry, University ofCoimbra, 3004-535 Coimbra, Portugal

[email protected]

Butanediols have numerous applications in biochemical research, namely in cryopreservation of living organs. The study of their molecular properties in different aggregation states is essential to understand their behavior. Their phase change thermodynamics have been previously studied by our research group, using theoretical calculations and calorimetric experiments. The detailed characterization of the non-associated states should provide helpful insights to the understanding their differences in vaporization and solvation energies.

1,4-butanediol is one of the most interesting isomers of these group of molecules. Having both hydroxyl groups in terminal positions, it can adopt stretched or folded conformations. The latter are characterized by the presence of intramolecular hydrogen bonds between the two terminal hydroxyl groups.

Matrix-isolation infrared spectroscopy is an ideal technique to explore the various conformations and hydrogen bond systems that can occur in non-associated states. In this work, 1-4-butanediol was deposited with different matrix gas hosts (Ar and Xe) and different optical substrate temperatures during matrix deposition (9 K for argon; 9 and 20 K for xenon).

Some difficulties arose from the intrinsically low intensity of the infrared absorptions of this compound. However, the spectra in xenon matrices showed the conversion, during the deposition phase, of some of the molecules to a different type of conformations having a different dominant type of hydrogen bonds. Based on these observations, we concluded that there is a different order of stability of conformers in the gaseous phase and in the low temperature matrix. It was possible to identify the corresponding two sets of infrared absorption bands in the registered spectra. The assignment of these bands to different conformers was made possible by the comparison with their predicted vibrational spectra by comprehensive DFT calculations at the B3LYP/6-311++G(d,p) level.


- 27 -

SL 9

The Structures of Some Small Clusters of Carbon Monoxide –

An Infrared Matrix Isolation Spectroscopic and ab initio Molecular Orbital Study

L. M. Nxumalo a, E. K. Ngidi b and T. A. Ford b

a Department of Chemistry, University of Johannesburg, Soweto Campus, Private Bag X09, Bertsham 2013, South Africab School of Chemistry, University of KwaZulu-Natal, Durban 4041, South Africa

[email protected]

Using the gas-phase structure of the dimer of carbon monoxide as a guide, ab initiomolecular orbital calculations have been carried out on this species in order to determine its probable structure in cryogenic matrices. The Fourier transform infrared spectra of carbon monoxide trapped in argon and nitrogen matrices have been recorded, and the observed spectra rationalized on the basis of the results of the theoretical calculations. The structure of the trimer of carbon monoxide has then been predicted, and a search for features attributable to the trimer in the matrix isolation spectra has been carried out.

This work was supported by the South African National Research Foundation under grant no. 2053648 and the University of KwaZulu-Natal Research Committee.


- 28 -

SL 10

Low Temperature Growth of Nanostructured Pb Film

Vladimir E. Bochenkov and Gleb B. Sergeev

Chemistry Dept. M.V. Lomonosov Moscow State University, Leninskie gory 1-3, Moscow 119992, Russia

[email protected]

Recently, the metallic nanoparticles have been successfully isolated in poly-p-xylylene matrix by using the low temperature codeposition of metal and p-xylylene vapors and further polymerization during annealing. It was found that the composite films, containing Pb nanoparticles are able to reversibly change their conductance in the presence of ammonia, which is of practical interest [1]. Closer study of these phenomena revealed that the Pb nanostructures, grown on the surface of poly-p-xylylene film, as well as on glass and alumina substrates, were also sensitive [2]. The sensitivity was found to appear near the percolation threshold of the Pb condensate [3].

In order to study the atomistic processes, taking place during the cryocondensation, the combined Molecular Dynamics (MD) – Temperature Accelerated Dynamics (TAD [4]) simulation was carried out. Using the TAD allowed us to simulate the deposition of Pb with typical rates (0.05 ML/s), used in our experiments. The dependence of film roughness and percolation threshold on deposition conditions is discussed.

[1] G. Sergeev, V. Zagorsky, M. Petrukhina, S. Zavyalov, E. Grigorev, and L.Trakhtenberg, Anal. Commun., 34 (1997) 113. [2] V. Bochenkov, V. Zagorsky, and G. Sergeev, Sensor. Act. B, 103 (2004) 375. [3] V. Bochenkov, P. Karageorgiev, L. Brehmer, and G. Sergeev, Thin Solid Films, 458 (2004) 303. [4] F. Montalenti and A. Voter, Phys. Rev. B, 64 (2001) 081401.

The work is supported by RFBR grant # 05-03-32293. The authors are grateful to A.Voter for TAD source code.


- 29 -

SL 11

Atomic Sodium Isolated in Rare-Gas Solids: A Comparison of Luminescence Spectroscopy and Molecular Dynamics Calculations

Maryanne Ryan a, Patrick dePujo b, Claudine Crépin c and John G. McCaffrey a

a Department of Chemistry, National University of Ireland Maynooth, County Kildare, Irelandb Laboratoire Francis Perrin, CEA Saclay 91191 Gif-sur-Yvette, Francec Laboratoire de Photophysique Moleculaire, Univ de Paris-Sud, 91405 Orsay France

[email protected]

The isolation of a metal atom in a rare-gas matrix at cryogenic temperatures results in a perturbation of the atomic electronic transition due to metal-matrix interactions. The nature of the trapping environment also has an effect on optical spectra obtained. A combined theoretical and experimental study is undertaken in order to understand the nature of these interactions. Absorption and luminescence excitation spectra, both steady-state and time-resolved, have been recorded [1] on atomic sodium (Na) isolated in the rare-gas solids argon, krypton and xenon. Computer simulations using classical molecular dynamics calculations have been performed for the three sodium/rare-gas systems. The purpose of the study is to (1) simulate the deposition of atomic Na in solid rare-gas matrices and (2) generate the absorption spectra of the resultant matrix-isolated metal atom samples. The absorption spectra generated with Na•RG interatomic potentials derived from both experiment [2] and ab initio calculations [3] reveal threefold splitting patterns in agreement with the recorded absorption spectra. Radial distribution functions calculated for the above systems, allow an identification of the sites of isolation of the Na atom in each matrix in the deposition simulations. Results to date indicate that the preferred site of occupancy in the argon matrix is a tetra-vacancy (tv), while that in xenon is found to be a substitutional site (ss). Two trapping sites, both tv and ss, have been simulated for the Na/Kr system.

[1] M. Quigley, M.Sc. Thesis NUI-Maynooth, 2002. [2] Baumann, P., Zimmermann, D., Bruhl, R., J. Mol. Spec., 155, 277 (1992). [3] Interatomic energy potential calculated by F. Spiegelman, private communication, 2004.

Work sponsored by the Irish Research Council for Science Engineering and Technology (IRCSET) Embark Initative Ph.D programme.


- 30 -

SL 12

Dynamics in Solid Parahydrogen Below 4 K

David T. Anderson

Department of Chemistry, University of Wyoming, Laramie, WY 82071-3838, USA

[email protected]

Cryogenic solid molecular hydrogen is a unique matrix isolation environment due to a variety of quantum mechanical effects such as large amplitude translational zero-point motion of the individual H2 molecules, the presence of ortho and para nuclear spin modifications, and that in the solid phase the individual molecules retain good vibrational and rotational quantum numbers. Equally intriguing is that a variety of non-classical dynamics occur within the crystal at liquid helium temperatures. This talk will highlight some of these dynamics as elucidated from high-resolution FTIR spectroscopy of chemically doped parahydrogen crystals. Some examples of the types of phenomena that have been studied are: ortho-H2 spin diffusion and cluster growth, nuclear spin relaxation of ortho-H2 to para-H2 catalyzed by the presence of a closed shell impurity molecule, and the loss of chemically reactive species introduced into the crystal via tunneling reactions with the surrounding H2.

This work is supported by a grant from the National Science Foundation (Grant No. CHE-0316268).


- 31 -

SL 13

Internal Rotation of CH3OH in Solid Parahydrogen

Yuan-Pern Lee a, b and Yu-Jong Wu c

a Dept. Applied Chemistry and Inst. Molecular Science, National Chiao Tung University, Hsinchu 30010, Taiwanb Institute of Molecular Sciences, Academia SInica, Taipei 106, Taiwanc Department of Chemistry, National Chiao Tung University, Hsinchu 30010, Taiwan

[email protected]

Even though molecules are more likely to rotate in solid parahyadrogen (p-H2) than in other inert gas matrices, vibration-rotational spectra of only a limited number of species have been reported. For species of larger size, perhaps internal rotation is more likely to take place than molecular rotation. We have investigated the infrared and far infrared absorption spectra of CH3OH isolated in solid p-H2 and compared with its spectra in the gaseous phase. In the C�O stretching region near 1031 cm�1, absorption lines split into four, as shown in Figure 1. The pairs (1030.5, 1030.8 cm-1) and (1031.0, 1031.3 cm-1) correspond to CH3OH in different matrix sites and each line in the parenthesis corresponds to the A and E component, respectively; the splitting into A and E components is due to internal rotation tunneling splitting. The splitting of 0.3 cm�1 is consistent with that reported for CH3OH in the gaseous phase. After allowing the matrix sample to be in the dark for a prolonged period, all lines relax to 1031.3 cm�1, indicating a nuclear-spin relaxation. The far infrared absorption spectrum of CH3OH in the region 200�400 cm�1 was also recorded. The preliminary data show an intense line at 355.9 cm�1 of H2 (J = 2 m J = 0) and weak lines at 202 and 298 cm

�1 that might be due to the torsional (internal rotational) mode of CH3OH. Further work is in progress.

1034 1032 1030 1028

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

Ab

so

rban

ce

Wave number / cm-1

After depositionAnneal at 4.2 K50 h at 3.2 K

Figure 1 – Absorption spectra of CH3OH at various stages: after deposition (dotted line), after annealing at 4.2 K (dashed line), and after sitting in the dark for 50 h (solid line).

[1] L.-H. Xu, R. M. Lees, P. Wang, L. R. Brown, I. Kleiner and J. W. C. Johns, J. Mol. Spectrosc., 228 (2004) 453. [2] R. M. Lees, L.-H. Xu, J. W. C. Johns, Z.-F. Lu, B. P. Winnewisser, M. Lock and R. L. Sams, J. Mol. Spectrosc., 228 (2004) 528.


- 32 -

SL 14

Ultrafast IR-Driven Cis-Trans Isomerization of Nitrous Acid

Virgiliu Botan, Roland Schanz, and Peter Hamm

Physikalisch Chemisches Institut, Universität Zürich, Winterthurerstr. 190, CH-8057 Zürich

[email protected], www.pci.unizh.ch

It is well established that electronically driven photochemistry is ultrafast in general. However, most (not all) chemistry is happening on electronic ground state potential energy surfaces, rather than through electronically excited states. From the experimental point of view, very little is known about the dynamics of ground state chemical reactions in the condensed phase on a microscopic, atomic level. The cis-trans isomerization of nitrous acid (HONO) in rare gas matrices is one of the few known photoreactions that can be triggered by IR excitation of one single vibrational quantum [1,2]. The molecule is well suited as a model system to study the dynamics of chemical reactions on electronic ground state potential surfaces. High level quantum dynamic calculations indicate that the reaction could not take place in the gas phase [3]. Hence, HONO furthermore appears to be a good candidate to examine the onset of condensed phase behaviour in chemical reactions.

Femtosecond pump-probe techniques have been applied to excite the OH stretching mode of the molecule and to track the progress of the photoreaction. Depletion of the cis-isomer and simultaneous creation of the trans-isomer is observed on a 20 picosecondtime-scale. In order to interpret and understand these observations on a qualitative level, quantum dynamical calculations have been performed. A model Hamiltonian is introduced that illustrates how the rare gas matrix couples the excited (OH-stretching) mode to the reactive (OH-torsional) mode [4].

Furthermore a new experiment was designed to observe the long time scale cooling of the products. Delays up to microseconds allowed us to obtain information on the dynamics of the isomerization. It can bee seen that after a 1ns certain mode is preferred and the excited population relaxes down to ground state staying in this particular mode following a well defined progression. New data were obtained about the back isomerization reaction (trans->cis), it’s dynamics and the quantum yield.

[1] A R. Hall, G. Pimentel, J. Chem. Phys., 1963, 38, 1889 [2] L. Khriachtchev, J. Lundell, E. Isoniemi, M. Räsänen, J. Chem. Phys., 2000, 113, 4265. [3] F. Richter, M. Hochlaf, P. Rosmus, F. Gatti, H.-D. Meyer, J. Chem. Phys., 2004,120,1306. [4] R. Schanz, V. Botan, P. Hamm, J. Chem. Phys., 2005, 122, 044509.

Source of funding: Swiss National Science Foundation


- 33 -

SL 15

Acetylacetone Trapped in Inert Matrices: UV and IR Photo-Induced Isomerizations and Theoretical Reactional Pathways

S. Coussan a, A. Trivella a, C. Manca b, Y. Ferro a, M. Rajzmann a, R. Wieczorek c, P. Piecuch d,e, K. Kowalski d, M. Włoch d, S.A. Kucharski d,f,

M. Musiał f and P. Roubin a

a Laboratoire de Physique des Interactions Ioniques et Moléculaires, UMR 6633, Université de provence-CNRS, Centre St-Jérôme, F-13397 Marseille Cedex 20, Franceb ETH Zürich, Laboratorium für Physikalische Chemie, ETH-Hönggerberg, HCI E 243 ,Wolfgang-Pauli-Str.10, CH-8093 Zürich , Switzerlandc Faculty of Chemistry, University of Wrocław, Joliot Curie 14, 50-383 Wrocław, Polandd Department of Chemistry, Michigan State University, east Lansing MI 48824, USAe Department of Physics and Astronomy, Michigan State University, east Lansing MI 48824, USAf Institute of Chemistry, University of Silesia, Szkolna 9, 40-006 Katowize, Poland

[email protected]

Acetylacetone and malonaldehyde (Fig.1) are the two simplest molecules which exhibit a strong intramolecular hydrogen bond with a proton tunneling exchange between the oxygen atoms. UV and IR-induced photoisomerizations of acetylacetone trapped in four different cryogenic matrices have been carried out using a tunable (UV and IR) OPO laser or a mercury lamp, and have been studied by UV and FTIR spectrometries. After deposition the main form of acetylacetone is the chelated form (enol). Upon UV irradiation the intramoleuclar H-bond is broken, leading to non-chelated forms. These forms have been irradiated, by resonant S o S* UV irradiation, or by resonant QOH IR irradiations. Interconversions between the non-chelated forms have been observed. Together with this experimental work, theoretical work was carried out in order to calculate the S0, S1and T1 electronic states geometries and harmonic frequencies (only for the S0 state), to calculate the UV transitions and to approach the reactional pathways. These calculations were performed at the ab initio (geometries, harmonic frequencies, UV transitions and reactional pathways) and semi-empirical (reactional pathways) levels of theory allowing us to greatly improve our vibrational assignments. The main results we have obtained lead us to suggest the existence of only 5 species on 8 in the matrix which display typical sets of vibrational and UV transition bands. The non-observation of 3 species is explained by the study of the reactional pathways. At last, the study of the kinetic constants of photoisomerization do not provide definitive argument about the real UV induced reactional pathways, i.e. a relaxation toward S0 through S1 or T1.

Figure 1: acetylacetone and malonaldehyde

O

C

C

C

O

H

RR

H

R = CH3 : acetylacetone

R = H : malonaldehyde


- 34 -

SL 16

The Photochemistry of Matrix Isolated Nitroso Derivatives

Jörg Glatthaar a and A. Reichenberg b

a Institute of Organic Chemistry, Justus-Liebig-University, Heinrich-Buff-Ring 58, 35392 Giessen, Germanyb Institute of Biochemistry, Justus-Liebig-University, Friedrochstrasse 24, 35392 Giessen, Germany

[email protected]

Nitroso hydrogen HNO and its derivatives are of growing interest in biochemical transformations [1]. They have been used in organic chemistry as reactants for synthetic applications [2,3]. Reports on the thermochemistry or the photochemistry of free nitroso hydrogen [4,5] and its derivatives [6] are rather scarce.

In this study it is shown that 9,10-dimet

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