Investigating the prolate-to-oblate shape phase transition: Lifetime measurements and γ spectroscopy of the low-lying negative parity structure in Os 193

Abstract

Excited states in Os193 were populated using a Os192(nth.,γ)Os193 thermal neutron capture reaction, with neutrons provided by the high-flux reactor of the Institut Laue-Langevin in Grenoble, France. Lifetimes of low-spin excited states were measured using the generalized centroid difference method. A total of eight mean lifetimes of low-lying excited states were determined for the first time, and limits for the lifetimes of three further excited states were established. Additionally, γ-γ angular correlations were analyzed to assign spins to previously known excited states up to 1 MeV, and extract multipole mixing ratios for several transitions. The new spectroscopic information is compared to calculations in the framework of the interacting boson-fermion model, based on the nuclear density functional theory, to investigate the prolate-to-oblate shape phase transition, predicted to occur in the neutron rich A≈190 region. © 2024 American Physical Society.