Nuclear moments of excited states. Recent results, developments and perspectives

Nuclear moments of excited states. Recent results, developments and perspectives.

• Nuclear moments of isomeric states – results ~ N=40• from projectile-fragmentation reactions (GANIL and MSU);

• How to reach the short-lived (<50 ns) isomers?• transfer reactions (Orsay)• developments

• deep-inelastic/multi-nucleon transfer regime – experiment to be performed soon in LNL

• What about the picoseconds states?• High-Velocity Transient Field (HVTF) at GANIL on the 2+ in 72Zn – work in progress• Can LNS contribute to the TF measurements?

• Summary and perspectives

G. Georgiev, CSNSM, Orsay

Introduction• Nuclear moments and their sensitivities:

• magnetic dipole moments • single-particle structure – proton/neutron character, active orbitals,

spin-flip contributions to the wave function

• electric quadrupole moments• collective properties and nuclear deformation

• Experimental methods and requirements• Time-Dependent Perturbed Angular Distribution

(TDPAD)• initial spin-aligned ensemble• external field for perturbation• change in the angular distribution

• Transient Field method • extremely high magnetic fields – many kTesla (provided by

the movement of the ions through a ferromagnetic host)

• Coulomb excitation with a particle-gamma correlations• observed change in the angular distribution


N=40 shell closure?

• High 2+ energy (R. Broda et al., PRL 74 868 (95))

• Low B(E2)(0+2+) value (O. Sorlin et al. PRL 88, 92501 (2002))

• Mass-measurements and S2n values show no kink at N=40 (C. Guenaut et al., PR C75, 44303 (07))

• Increased collectivity with addition of just two particles.(O. Perru et al. PRL 96, 232501 (2006))

• Our approach – probing the purity of the wave functions and the deformation through nuclear moment measurements


TDPAD on 67Ni and 69Cu @ GANIL 1999

• g(69Cu)exp. = 0.225(25)• g(67Ni )exp. = 0.125(6)

low signal-to-noise ratio

First measurement in projectile fragmentation

G. Georgiev et al., JP G28, 2993 (2002)


Magnetic and quadrupole moments of 61mFe

g(61Fe,9/2+) =-0.229(2)I.Matea et al., PRL 93, 142503 (2004)

654 keV

207 keV

|Qs(61Fe,9/2+)| = 0.41(6) bN. Vermeulen et al., PR C75, 51302 (2007)

First Q moment measurement in projectile fragmentation


Beyond N=40 – 70Ni at MSU

g (70Ni)exp. = -0.320 (15)

• 76Ge beam @ 130 MeV/u• 9Be target• A1900 fragment separator ~90% beam purity• 4 SeGA detectors•data for 70Ni taken during ~12 hours


65Ni in transfer reaction - Orsay

Ge BaF2

g(65Ni)exp. = - 0.296(3) G. Georgiev et al., EPJ A30, 351 (2006)

• (d,p) reaction• 2 Ge and 2 BaF2 detectors• enriched 64Ni/62Ni (ferromagnetic) target


Comparison experiment vs. theory

LSSM calculations using 48Ca core and free-nucleon g factors:

• very good agreement with 63Ni, 65Ni• significant contributions from protonexcitations across Z=28• 61Fe – less well reproduced

63Ni, 65Ni, 70Ni and 61Fe fitting well in the g9/2 g-factor systematics in the region

S.Lunardi et al., PR C76, 34303 (2007)N.Hoteling et al., PR C77, 44314 (2008)

g factors

Vermeulen et al., PR C75, 51302 (2007)

Q moment• LSSM calculations with canonicaleffective charges reproduce well the experimentally determined Q moment• Two possible scenarios in mean-fieldcalculations K = 1/2 or K = 9/2 withvery similar quadrupole momentsQs = -0.36 b vs. Qs = -0.46 bQexp. = |0.41(6)| bSpectroscopic studies of the isomeric

band point towards prolate defformation


How to reach the shorter-lived isomers?

E. Fiori, M.Sc. Thesis, Univ. Camerino

• Spin alignment in deep-inelastic reactionsSpin alignment in deep-inelastic reactions previously observedpreviously observed T. Pawlat T. Pawlat et et al.al., LNL Ann. Rep. (1994) 8, LNL Ann. Rep. (1994) 8 • 3232S beam on S beam on 4040Ca target well above Ca target well above the CBthe CB• strong alignment observed for for 43m43mScSc

• 335 MeV 335 MeV 7676Ge on Ge on 7070Zn target Zn target (Ni or Au backing)• 4 Ge detectors in a horizontal plane4 Ge detectors in a horizontal plane• electromagnet electromagnet (0.05 – 0.7 T)

Experiment to be Experiment to be performed at performed at

LNL within the next LNL within the next few monthsfew months


g factors of 2+ states around N=40 – what can we learn?

• Ni (Z=28) – semi-magic nuclei

• Zn (Z=28+2)• Z/A up to N=40 for the 2+

• Ge (Z=28+4) – consistent with

Z/A line

Theories (Strasbourg-Madrid; M. Hjorth-Jensen; B.A. Brown et al.) predict a deviation from Z/A – can it be observed experimentally and where?

-0.4

-0.2

0

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28 30 32 34 36 38 40 42 44 46 48 50

Neutron number

g fa

ctor

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28 30 32 34 36 38 40 42 44 46 48 50

Neutron number

g fa

ctor

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28 30 32 34 36 38 40 42 44 46 48 50

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g fa

ctor

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28 30 32 34 36 38 40 42 44 46 48 50

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ctor

g factors of 2+ states – a measure for the interplay between the single-particleand collective properties in the nuclei


The TF method

A.E. Stuchbery, PR C69, 64311 (2004)

(Z)st) · B (v, Z, ho q(Z,host) ·pGB sssattTF 111

beam

+

-±

Bext

Bg N

L

Larmor frequency

/g = (N·B·teff)/ħ

Precession angle: = Lteff

• Gatt. – empirical att. factor

• B1s = 16.7*K*Z3 Tesla

• q1s- H-like fraction

• p1s ???


Experimental setup

determination of θ

angular distribution

particledetector

3°<α<5.5°

mask

target

beam(105 p/s)

25°

125°

155°

-60°

90°

-25°

-125°

-155°


72Zn and 76Ge – work in progress

GeGe

Zn

TF

TFZn g

GeBZnBg

)()(

θGe = 11 ± 5 mrad θZn = 16 ± 5 mrad

• g(2+, 72Zn) – very similar to the one of 76Ge• B(HVTF) of Zn/Ge in Gd – 5 times smaller than expected (cause p1s)• B(HVTF) of Zn/Ge in Fe – no effect observed


TF and LNS?

@LNS

A systematic study of Btf as a function of Z and vion is of crucial importance


Summary and perspectives

• g factors - very sensitive probes for small g factors - very sensitive probes for small admixtures in the nuclear wave functionsadmixtures in the nuclear wave functions

• g(2g(2++) fingerprint of the interplay between ) fingerprint of the interplay between collective and single-particle propertiescollective and single-particle properties

• Q moments – direct information on the Q moments – direct information on the deformation deformation

• Developments are on the way and still more Developments are on the way and still more need to be done in order to reach more and need to be done in order to reach more and more exotic nucleimore exotic nuclei


Collaborations• CSNSM, Orsay, France

E. Fiori, R. Lozeva, S. Cabaret• University of Camerino, Camerino, Italy and INRNE, BAS, Bulgaria*

D.L. Balabanski*, G. Lo Bianco, A. Saltarelli• CE Bruyères le Châtel, France

J.M. Daugas, G. Belier, V. Meot, O. Roig• The Weizmann Institute of Science, Israel

M. Hass, G. Goldring, N.S. Bondilli, V. Kumar• GANIL, Caen, France

E. Clement, G. De France, F. De Oliveira Santos, S. Grevy, M. Lewitowicz, C. Stodel• Department of Nuclear Physics, ANU, Canberra, Australia

A. Stuchbery• Dep. Física Teórica, Univ. Autónoma de Madrid, Spain

A. Jungclaus, V. Modamio, J. Walker• CENBG, Bordeaux-Gradignant, France

I. Matea, M. Tarisien• IKS, KU Leuven

G. Neyens, N. Vermeulen, D. Yordanov• IPN, Orsay, France

S. Franchoo, F. Ibrahim, F. Le Blanc, B. Mouginot, L. Perrot, O. Sorlin, I. Stefan, M. Stanoiu, D. Verney• NSCL, MSU, USA

P. Mantica, W. Mueller, T. Ginter, M. Hausman, A. Stolz• FLNR, JINR, Dubna, Russia

S. Lukyanov, Yu. Penionzhkevich, Yu. Sobolev• ISK, Universitaet Bonn, Germany

K.H. Speidel, J. Leske• IKS, Univ. Cologne, Germany

A.Blazhev• University of Sofia, Bulgaria

M. Danchev• Univ. Ioannina, Greece

T. Mertzimekis



Experimental conditions

Snow at GANIL in April???

Documents

Nuclear moments of excited states. Recent results, developments and perspectives