Physique Nucléaire

C. Delafosse "Study of neutron monopole drift toward 78Ni and first lifetime measurements in the 78Ni region with AGATA and VAMOS at GANIL"

Europe/Paris
Bat 27
Description

Yrast and near-Yrast states were populated in the 78Ni region by fusion-ssion reaction 238U(9Be,X) at GANIL. The prompt-rays
were detected by the AGATA arraya and particle identication was achieved using the VAMOS++ spectrometerb. Lifetime
measurements were performed using the Recoil Distance Doppler Shift technique developed at Colognec with the Orsay
plunger device OUPS.
The goal of the experiment was to populate Yrast states in N=51 neutron-rich odd-isotones from 89Sr (Z = 38) down to
83Ge (Z = 32) in order to study the high-` single-particle states eective energy evolution above the N = 50 shell gap and
complement the scarce direct nucleon exchange data presently availablee. These reactions are indeed dicult to exploit with
presently available post-accelerated radioactive ion beams (especially for high-` orbitals) in this exotic region. More specically,
we have focused our attention on the 1g7=2 monopole drift which is 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. Our strategy was to measure low
lying 7=2+ states life times as their relative change along the N = 51 line towards Z = 28 should reect their possible 1g7=2
composition. The tensor mechanismf indeed predicts increasingly large 1g7=2 single-particle components in the low-lying 7=2+
states wavefunctions approaching 79Ni.