Softness and shape coexistence in the light platinum isotopes

Abstract

Data have recently been presented that were interpreted as evidence for shape coexistence in platinum-176. The authors re-examine these data using the dynamic deformation model of Kumar (1984) to calculate the potential energy surfaces (PES). These indicate that all the platinum isotopes are gamma soft and some are also beta soft. The PES show platinum-176 to be a transitional nucleus for both the Z=78 isotopes and the N=98 isotones, with an extremely flat minimum with respect to both beta and gamma deformations. This softness may account for its anomalous experimental level spacing in the yrast band. The interpretation of softness is supported by interacting boson approximation calculations made for this region, and by results obtained from the variational moment of inertia model. Differences between this interpretation and that of shape coexistence are discussed.