Speaker
Description
Experimental studies of excited states have been performed to probe the evolution of the shell structure in neutron-rich nuclei. In the case of N=50 isotopes from 90Zr to 78Ni, specific excited states correspond mainly to neutron excitations across the N=50 gap. Thus, the evolution of the excitation energy of these states, particularly in the 82Ge nuclei, enables to deduce the size of the N=50 gap. In addition, information on the collective or single-particle (particle - hole configuration) nature may be obtained in odd Ge isotopes on both sides of the N=50 gap (81Ge and 83Ge).
A large data set of neutron-rich nuclei is produced in a fusion-fission reaction with 238U beam (at 6.2 MeV/u) impinging a 9Be target. The several fission fragments are selected unambiguously (A and Z identification) by the VAMOS++ spectrometer. The prompt gamma rays are detected in coincidence with the fission fragments by the AGATA array composed of 8 triple-clusters.
The experimental results are compared with the most advanced shell-model calculations using the most updated interaction for this region in the nuclear chart.
The structure of these N=49 and N=51 nuclei has already been investigated through beta-decay, Coulomb excitation, and nucleon-transfer experiments. However, their high-spin states have not yet been studied using prompt gamma-ray spectroscopy. Indeed, for the first time, the level schemes of various neutron-rich Ge isotopes (N=49, N=50, and N=51) and 79Zn (N=49) will be presented and discussed in the light of theoretical calculations.