High-spin states inAu191,193andPt192: Evidence for oblate deformation and triaxial shapes

Abstract

High-spin states of $^{191,193}\mathrm{Au}$ and $^{192}\mathrm{Pt}$ have been populated in the $^{186}\mathrm{W}$($^{11}\mathrm{B}$, xn) and $^{186}\mathrm{W}$($^{11}\mathrm{B}$, p4n) reactions, respectively, at a beam energy of 68 MeV and their \ensuremath{\gamma} decay was studied using the YRAST Ball detector array at the Wright Nuclear Structure Laboratory at Yale University. The level scheme of $^{193}\mathrm{Au}$ has been extended up to ${I}^{\ensuremath{\pi}}=55/{2}^{+}$. New transitions were observed also in $^{191}\mathrm{Au}$ and $^{192}\mathrm{Pt}$. Particle-plus-Triaxial-Rotor (PTR) and Total Routhian Surface (TRS) calculations were performed to determine the equilibrium deformations of the Au isotopes. The predictions for oblate deformations in these nuclei are in agreement with the experimental data. Development of nonaxial shapes is discussed within the framework of the PTR model.