mardi 3 mars 2020 à 14:00
While the N=50 shell-gap evolution towards 78Ni is presently in the focus of nuclear structure research, experimental information on the neutron effective single particle energy (ESPE) sequence above the 78Ni core remain scarce. Direct nucleon exchange reactions are indeed difficult with presently available post-accelerated radioactive ion beams (especially for high orbital momentum orbitals) in this exotic region. We have studied the evolution of the νg7/2 ESPE which is the key to understanding the possible evolution of the spin-orbit splitting due to the action of the proton-neutron interaction terms in the 78Ni region by measuring the lifetime of excited states in order to distinguish between collective and single-particle states. The evolution of the ESPE of this orbital, characterized by a high orbital momentum l=4, should indeed be particularly sensitive to tensor effects.
In the continuity of an experiment performed in LNL-Legnaro , we performed an experiment at GANIL (Caen, France) with AGATA , VAMOS  and the Orsay plunger OUPS  in order to measure lifetime of Yrast excited states (in peculiar 7/21+ states) in several N=51 isotones populated by the reaction 238U(9Be,f). We particularly focused our study on 83Ge, the closest N=51 odd isotones to 79Ni for which detailed spectroscopy studies are possible within our experimental conditions. We also performed complementary β-delayed γ spectroscopy of 83Ge with BEDO  at the ALTO ISOL photo-fission facility in Orsay to investigate non-Yrast spectroscopy.
Results from both experiments as well as on-going work at IGISOL will be presented and discussed.
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