Probing core polarization around 78Ni: intermediate energy Coulomb excitation of 74Ni
1 INFN Legnaro National Laboratories, Legnaro (Pd), Italy
2 Department of Physics, Padua University, Padua, Italy
3 NSCL, Michigan State University, East Lansing, Michigan 48824-1421, USA
4 INFN Pisa, Pisa, Italy
5 Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
6 INFN Naples, Naples, Italy
7 Physics Department, Naples University Federico II, Italy
8 Physics Department, Deenbandhu Chhoturam University, Murthal, Sonepat, Haryana 131039, India
9 Ionizing Radiations Laboratory, University of Salamanca, Spain
10 INFN Padua, Padua, Italy
11 CSIC-IFIC, Valencia, Spain
a e-mail: firstname.lastname@example.org
Published online: 19 December 2013
The study of the evolution of nuclear shells far from stability provides fundamental information about the shape and symmetry of the nuclear mean field. Nuclei with large neutron/proton ratio allow to probe the density dependence of the effective interaction. Indeed, it was recently shown that tensor and three-body forces play an important role in breaking and creating magic numbers. Of particular interest is the region of 78Ni where the large neutron excess coincides with a double shell closure.
We have recently measured the B(E2; 0+ → 2+) of the 74Ni nucleus in an intermediate-energy Coulomb excitation experiment performed at the National Superconducting Cyclotron Laboratory of the Michigan State University. The 74Ni secondary beam has been produced by fragmentation of 86Kr at 140 AMeV on a thick Be target. Selected radioactive fragments impinged on a secondary 197Au target where the measurement of the emitted γ-rays allows to extract the Coulomb excitation cross section and related structure information. Preliminary B(E2) values do not point towards an enhancement of the transition matrix element and the comparison to what was already measured by Aoi and co-workers in  opens new scenarios in the interpretation of the shell evolution of the Z=28 isotopes.
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