Lifetime measurement of high spin states in non-yrast bands in¹⁷⁷Re

Abstract：

The deformation driving tendency of various single particle orbitals near the Fermi surface has been investigated with the lifetime measurements of high spin states in the non-yrast bands of $^{177}{\rm Re}$ nucleus. For this study, the $^{165}{\rm{Ho}}$ ( $^{16}{\rm{O}}$ , 4n) $^{177}{\rm{Re}}$ reaction at a beam energy of 84 MeV was used. Lifetimes of four lowest levels in the $\pi i_{13/2}[660]1/2^+$ band and four levels in the $\pi d_{5/2}[402]5/2^+$ ( α= –1/2) band were measured. The extracted transition quadrupole moments for the $\pi i_{13/2}$ intruder band showed a sharp increase with increasing level spin, indicating a significant shape transition in the nucleus. The average transitional quadrupole moment ( $Q_t$ ), a measure of deformation, for the $\pi i_{13/2}$ band was significantly larger ( $Q_t$ ~ 8.7 (6) eb) compared with the $\pi d_{5/2}$ ( $Q_t$ ~ 6.3 (5) eb) band. To interpret the observed shape changes in the two bands, the experimental transition probabilities for these bands were compared with the results obtained from Projected Shell Model (PSM) calculations.