Lifetimes of states in the opposite-parity bands of153Eu:Recoil-distance measurements following Coulomb excitation

Abstract

The lifetimes of 12 states in the opposite-parity bands of ${}^{153}\mathrm{Eu}$ have been measured using a recoil-distance technique following Coulomb excitation with a 220-MeV ${}^{58}\mathrm{Ni}$ beam. Electric-quadrupole ${(Q}_{0})$ and -dipole ${(D}_{0})$ moments, and intrinsic g factors ${(g}_{K})$ have been extracted from the lifetimes. The ${Q}_{0}$ and ${D}_{0}$ values show very little dependence on spin and parity, and have the values of approximately 6.6 e b and 0.077 e fm, respectively. The ${g}_{K}$ values are found to differ for the positive- and negative-parity states. Although the large ${D}_{0}$ values suggest a reflection-asymmetric octupole-deformed nuclear shape, the different ${g}_{K}$ values contradict this interpretation. A discussion of the nuclear structure of ${}^{153}\mathrm{Eu}$ in terms of potential parity-doublet bands and octupole deformation is given.