Systematic Cranked Shell Model Calculations for ${}^{87,89,91}$Br

Abstract

A systematic investigation of the odd-mass neutron-rich bromine isotopes ${}^{87-91}$Br has been carried out within the configuration-constrained cranked shell model (CSM) framework. The calculated kinematic moments of inertia and angular-momentum alignments reproduce the experimental trends with excellent agreement for the proposed quasiparticle configurations, thereby supporting the assigned band structures. The total Routhian surface calculations reveal pronounced ${\hat{I}}^3$-softness in ${}^{87}$Br, shape coexistence in ${}^{89-93}$Br, and a gradual prolate-to-oblate transition approaching $N=56$. These results demonstrate that the CSM provides a reliable description of rotational behavior and shape evolution in this mass region, achieving a better level of accuracy, while offering a transparent interpretation of quasiparticle configurations and shape-driving effects.

12 pages, 6 figures