Measurement of lifetimes in Fe62,64,Co61,63 , and Mn59

M Klintefjord,E Clément,D Ralet,F Recchia,P Désesquelles,M Zielińska,S M Lenzi,H Hess,D Barrientos,L Charles,J Nyberg,F L Bello Garrote,C Fransen,I Stefan,B Birkenbach,D Mengoni,Ch Theisen,D T Doherty,A Gengelbach,J Dudouet,A Pullia,J Libert,A Jungclaus,A Korichi,A E Stuchbery,J Eberth,G De France,R Menegazzo,R M Pérez-Vidal,M Girod,A Goasduff,V González,A Görgen,J Ljungvall,C Michelagnoli,A Gottardo,B Million,A Navin,S Roccia,M D Salsac,A Gadea,P Reiter,A Lemasson,B Jacquot,T Konstantinopoulos,A Blazhev,E Šahin ,A J Boston ,M Ciemała ,W Körten ,L J Harkness-Brennan ,O Stézowski ,Α Dewald ,J.p Delaroche ,E Sanchís ,K Hadyńska-Klȩk ,А Лопез-Мартенс ,Г Георгиев ,J J Valiente Dobón

doi:10.1103/physrevc.95.024312

Abstract

Lifetimes of the 41+ states in 62,64Fe and the 11/21− states in 61,63Co and 59Mn were measured at the Grand Accelerateur National d'Ions Lourds (GANIL) facility by using the Advanced Gamma Tracking Array (AGATA) and the large-acceptance variable mode spectrometer (VAMOS++). The states were populated through multinucleon transfer reactions with a U238 beam impinging on a Ni64 target, and lifetimes in the picosecond range were measured by using the recoil distance Doppler shift method. The data show an increase of collectivity in the iron isotopes approaching N=40. The reduction of the subshell gap between the ν2p1/2 and ν1g9/2 orbitals leads to an increased population of the quasi-SU(3) pair (ν1g9/2,ν2d5/2), which causes an increase in quadrupole collectivity. This is not observed for the cobalt isotopes with N<40 for which the neutron subshell gap is larger due to the repulsive monopole component of the tensor nucleon-nucleon interaction. The extracted experimental B(E2) values are compared with large-scale shell-model calculations and with beyond-mean-field calculations with the Gogny D1S interaction. A good agreement between calculations and experimental values is found, and the results demonstrate in particular the spectroscopic quality of the Lenzi, Nowacki, Poves, and Sieja (LNPS) shell-model interaction.

Highlights

A cornerstone of nuclear structure physics is the existence of “magic” nuclei with increased binding due to large gaps in the single-particle shell structure
A good agreement between calculations and experimental values is found, and the results demonstrate in particular the spectroscopic quality of the Lenzi, Nowacki, Poves, and Sieja (LNPS) shell-model interaction
Spectroscopy of exotic nuclei away from the line of β stability has shown that the magic numbers are not universal throughout the nuclear chart but depend on the ratio of neutron to proton numbers; that is, they may vary as a function of isospin [1]

Summary

Introduction

A cornerstone of nuclear structure physics is the existence of “magic” nuclei with increased binding due to large gaps in the single-particle shell structure. Spectroscopy of exotic nuclei away from the line of β stability has shown that the magic numbers are not universal throughout the nuclear chart but depend on the ratio of neutron to proton numbers; that is, they may vary as a function of isospin [1]. Far from stability, the relative strength of the different terms in the nuclear force may vary and cause a modification of the shell structure. Regions in the nuclear chart with rapid changes in collectivity as a function of Z or N are of particular interest because they allow stringent testing of theoretical models. The neutron-rich nuclei close to 68Ni show a rapid variation in collectivity, which is understood in the shell model as the combination of the effect of the monopole part of the central and tensor force [2,3], leading to a reduced shell gap at

Results

Discussion

Conclusion