The O(6) → rotor transition in the PtOs nuclei

Abstract

Abstract The PtOs nuclei are treated from the viewpoint of the interacting boson approximation model, in particular, as a region initiating an O(6) → rotor transition. It is found that the levels and level patterns predicted in the O(6) limit occur in these nuclei and that the trends in a large number of rapidly varying B (E2) values and E2 branching ratios can be reproduced by calculations that are sensitive almost solely to a single parameter representing the relative location of a nucleus between the O(6) and rotor extremes. This parameter is chosen to vary smoothly and systematically. Specifically, the striking empirical differences in the decay modes of 0 + states in Pt and Os emerge as natural and nearly parameter independent consequences of the changes in boson number with mass. Other characteristics features of the O(6) → rotor transition, such as the behavior of 0 + −2 + −2 + sequences, the emergence of K = 4 rotational bands in Os and the rapidly changing branching ratios involving the quasi-γ-band all reflect corresponding empirical trends in this region. Further, the perturbed O(6) scheme predicts absolute B (E2) values which, over the entire region, agree much better with the data than those of existing models.