Softness and shape coexistence in the light platinum isotopes

Data have recently been presented that were interpreted as evidence for shape coexistence in platinum-176. These data are reexamined using the dynamic deformation model to calculate the potential energy surfaces (PESS). These indicate that all the platinum isotopes are γ soft and some are also β soft. The PESS show platinum-176 to be a transitional nucleus for both the ZETA 78 isotopes and the NU = 98 isotones, with an extremely flat minimum with respect to both β and γ 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. (author)