Triaxial projected shell model study of the rapid changes inB(E2)for180−190Pt isotopes

The mass region with a proton number just below the magic number $Z=82$ is known to exhibit a rich variety of shape phenomena. Inspired by the recent extensive experimental measurements of the transition probabilities for the yrast bands in some Pt isotopes in this mass region, we have performed a detailed investigation of ${}^{180\ensuremath{-}190}$Pt using the triaxial projected shell model approach (TPSM). It is demonstrated that by performing the exact three-dimensional angular-momentum projection on multi-quasiparticle configurations, constructed from the traxially deformed mean field, the TPSM provides a consistent description of the yrast band structures, the $\ensuremath{\gamma}$-vibrational band, and the second ${0}^{+}$ band in these nuclei. Further, the observed rapid variations in the quadrupole transition probability along the yrast line of these isotopes are well reproduced in the present study.