1 / 18

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

craig
Download Presentation

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

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 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

  2. 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

  3. 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

  4. TDPAD on 67Ni and 69Cu @ GANIL 1999 First measurement in projectile fragmentation low signal-to-noise ratio • g(69Cu)exp. = 0.225(25) • g(67Ni )exp. = 0.125(6) G. Georgiev et al., JP G28, 2993 (2002)

  5. 654 keV 207 keV Magnetic and quadrupole moments of 61mFe First Q moment measurement in projectile fragmentation |Qs(61Fe,9/2+)| = 0.41(6) b g(61Fe,9/2+) =-0.229(2) N. Vermeulen et al., PR C75, 51302 (2007) I.Matea et al., PRL 93, 142503 (2004)

  6. Beyond N=40 – 70Ni at MSU • 76Ge beam @ 130 MeV/u • 9Be target • A1900 fragment separator ~90% beam purity • 4 SeGA detectors • data for 70Ni taken during ~12 hours g (70Ni)exp. = -0.320 (15)

  7. Ge BaF2 65Ni in transfer reaction - Orsay • (d,p) reaction • 2 Ge and 2 BaF2 detectors • enriched 64Ni/62Ni (ferromagnetic) target g(65Ni)exp. = - 0.296(3) G. Georgiev et al., EPJ A30, 351 (2006)

  8. Comparison experiment vs. theory g factors Q moment 63Ni, 65Ni, 70Ni and 61Fe fitting well in the ng9/2 g-factor systematics in the region • 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)| b Vermeulen et al., PR C75, 51302 (2007) Spectroscopic studies of the isomeric band point towards prolate defformation • 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 S.Lunardi et al., PR C76, 34303 (2007) N.Hoteling et al., PR C77, 44314 (2008)

  9. Experiment to be performed at LNL within the next few months E. Fiori, M.Sc. Thesis, Univ. Camerino How to reach the shorter-lived isomers? • Spin alignment in deep-inelastic reactions previously observedT. Pawlat et al., LNL Ann. Rep. (1994) 8 • 32S beam on 40Ca target well above the CB • strong alignment observed for 43mSc • 335 MeV 76Ge on 70Zn target (Ni or Au backing) • 4 Ge detectors in a horizontal plane • electromagnet (0.05 – 0.7 T)

  10. g factors of 2+ states around N=40 – what can we learn? g factors of 2+ states – a measure for the interplay between the single-particleand collective properties in the nuclei • Ge (Z=28+4) – consistent with Z/A line • Ni (Z=28) – semi-magic nuclei • Zn (Z=28+2) • Z/A up to N=40 for the 2+ Theories(Strasbourg-Madrid; M. Hjorth-Jensen; B.A. Brown et al.) predict a deviation from Z/A – can it be observed experimentally and where?

  11. ±q - Bext beam + Larmor frequency  A.E. Stuchbery, PR C69, 64311 (2004) The TF method Precession angle:q = Lteff q/g = (N·B·teff)/ħ • Gatt. – empirical att. factor • B1s = 16.7*K*Z3 Tesla • q1s- H-like fraction • p1s???

  12. determination of θ 90° 125° angular distribution 25° 155° beam (105 p/s) mask particle detector 3°<α<5.5° -155° -25° target -125° -60° Experimental setup

  13. 72Zn and 76Ge –work in progress 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

  14. @LNS TF and LNS? A systematic study of Btf as a function of Z and vion is of crucial importance

  15. Summary and perspectives • g factors - very sensitive probes for small admixtures in the nuclear wave functions • g(2+) fingerprint of the interplay between collective and single-particle properties • Q moments – direct information on the deformation • Developments are on the way and still more need to be done in order to reach more and more exotic nuclei

  16. Collaborations • CSNSM, Orsay, FranceE. 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, FranceJ.M. Daugas, G. Belier, V. Meot, O. Roig • The Weizmann Institute of Science, IsraelM. Hass, G. Goldring, N.S. Bondilli, V. Kumar • GANIL, Caen, FranceE. Clement, G. De France, F. De Oliveira Santos, S. Grevy, M. Lewitowicz, C. Stodel • Department of Nuclear Physics, ANU, Canberra, AustraliaA. Stuchbery • Dep. Física Teórica, Univ. Autónoma de Madrid, SpainA. Jungclaus, V. Modamio, J. Walker • CENBG, Bordeaux-Gradignant, FranceI. Matea, M. Tarisien • IKS, KU LeuvenG. Neyens, N. Vermeulen, D. Yordanov • IPN, Orsay, FranceS. Franchoo, F. Ibrahim, F. Le Blanc, B. Mouginot,L. Perrot,O. Sorlin, I. Stefan, M. Stanoiu, D. Verney • NSCL, MSU, USAP. Mantica, W. Mueller, T. Ginter, M. Hausman, A. Stolz • FLNR, JINR, Dubna, RussiaS. Lukyanov, Yu. Penionzhkevich, Yu. Sobolev • ISK, Universitaet Bonn, GermanyK.H. Speidel, J. Leske • IKS, Univ. Cologne, GermanyA.Blazhev • University of Sofia, BulgariaM. Danchev • Univ. Ioannina, GreeceT. Mertzimekis

  17. Experimental conditions Snow at GANIL in April???

More Related