Orateur
Dr
Mohamad Moukaddam
(Université de Strasbourg, IPHC, 23 rue du Loess, F-67037 Strasbourg, France, CNRS, UMR7178, F-67037 Strasbourg, France)
Description
It has been shown that the neutron 2d5/2 orbital has to be included in shell-model calculations to explain the appearance of large quadrupole collectivity observed in the neutron rich Fe and Cr of the N ≈ 40 region. This work initiated by Caurier et al. has been recently revisited. Calculations in a large valence space involving the fp proton shell and the fpgd neutron shells including a strongly
reduced 1g9/2 - 2d5/2 neutron gap down to ≈ 1.5 MeV affect the whole N = 40 region and point out a new island of inversion similar to those known for light nuclei around N = 8 and N = 20. A global mecanism could be deduced, in the frame of the shell-model approach, of the emergence of islands of inversion at Harmonic-Oscillator shell gaps driven by two particle-two hole neutron excitations into quadrupole-partner orbitals across these gaps.
Since now, no 5/2+ state has been assigned in previous studies of 69Ni, an ideal laboratory to search for the neutron 2d5/2 orbital. A (d,p) reaction onto a 68Ni beam produced at GANIL has been used to probe the single-particle energy of the 2d5/2 neutron orbital in 69Ni. Two 5/2+ states with important spectroscopic factors lying around 2.5 MeV excitation energy have been observed, for the first time, in 69Ni. The doublet is understood as the mixing of two main configurations of spherical nature. These results are in good agreement with large-scale shell-model calculations in which 2.5 MeV 1g9/2 - 2d5/2 gap for neutrons is included, and confirm experimentally Caurier’s assumption of a reduced 1g9/2 - 2d5/2 neutron gap at N = 40.
Auteurs principaux
Dr
Didier Beaumel
(IPN , CNRS/IN2P3, Université Paris-Sud, F-91406 Orsay, France)
Dr
Gilbert Duchêne
(Université de Strasbourg, IPHC, 23 rue du Loess, F-67037 Strasbourg, France, CNRS, UMR7178, F-67037 Strasbourg, France)
Dr
Mohamad Moukaddam
(Université de Strasbourg, IPHC, 23 rue du Loess, F-67037 Strasbourg, France, CNRS, UMR7178, F-67037 Strasbourg, France)
Co-auteurs
Dr
Alain Gillibert
(CEA-Saclay/ IRFU / SPhN)
Dr
Alexandre Obertelli
(CEA/DSM/IRFU/SPhN)
Dr
Beatriz FERNANDEZ-DOMINGUEZ
(GANIL)
Dr
Christelle Stodel
(GANIL)
Dr
Christian Finck
(CNRS)
Dr
Dominique CURIEN
(IPHC)
Mlle
Else Pllumbi
(IPNO)
Dr
Emmanuel Clement
(CNRS GANIL)
Dr
FLORENT HAAS
(IPHC STRASBOURG)
Dr
Faïrouz Hammache
(IPN-Orsay)
Dr
Francois DIDIERJEAN
(IPHC)
Dr
Freddy FLAVIGNY
(CEA-Saclay/ IRFU / SPhN)
Dr
Frederic NOWACKI
(IPHC Strasbourg)
Dr
GEOFFROY BURGUNDER
(GANIL, CEA/DSM-CNRS/IN2P3, Bd Henri Becquerel, F-14076 Caen, France)
Dr
Iolanda MATEA
(IPN Orsay)
Dr
Iulian stefan
(Institut de Physique Nucléaire (IPN))
Dr
Jacques Guillot
(IPNO)
Dr
Jean-Claude Thomas
(GANIL)
Dr
Julien Gibelin
(LPCCaen)
Dr
Julien Pancin
(GANIL)
M.
Julien Piot
(IPHC Strasbourg)
Dr
Kamila Sieja
(Institute Pluridisciplinaire Hubert Curien)
Prof.
Kerby Kemper
(Department of Physics, Florida State University, Tallahassee, Florida 32306, USA)
Dr
Laurent Nalpas
(CEA/Saclay - IRFU - SPhN)
Dr
Luc Perrot
(IPNO)
Dr
Lucia Caceres
(GANIL, CEA/DSM-CNRS/IN2P3, Bd Henri Becquerel, F-14076 Caen, France)
Prof.
Muhsin N. Harakeh
(GSI/KVI)
Dr
Nicolas de Sérévile
(IPNO)
Dr
Olivier Sorlin
(GANIL)
M.
Riccardo Raabe
(GANIL Caen)
Dr
Sandra GIRON
(IPNO)
Dr
Stéphane Grévy
(GANIL)
Dr
Valérie Lapoux
(CEA/Saclay - IRFU - SPHN)
M.
adrien matta
(IPNOrsay)
jean-antoine scarpaci
(IN2P3)
serge franchoo
(ipn)
