Microscopic Description of Spherical to Gamma-Soft Shape Transitions in Ba and Xe Nuclei

TL;DR

This paper investigates the shape transition in Ba and Xe nuclei from spherical to gamma-soft configurations using a microscopic model, revealing a second-order phase transition consistent with E(5) symmetry.

Contribution

It introduces a microscopic approach combining relativistic mean-field calculations with a five-dimensional Hamiltonian to describe shape transitions in nuclei.

Findings

Reproduces excitation spectra and E2 transition probabilities accurately.

Identifies fingerprints of a second-order shape phase transition.

Shows spectra consistent with E(5) dynamical symmetry.

Abstract

The rapid transition between spherical and $\gamma$-soft shapes in Ba and Xe nuclei in the mass region $A \geq 130$ is analyzed using excitation spectra and collective wave functions obtained by diagonalization of a five-dimensional Hamiltonian for quadrupole vibrational and rotational degrees of freedom, with parameters determined by constrained self-consistent relativistic mean-field calculations for triaxial shapes. The results reproduce the characteristic evolution of excitation spectra and E2 transition probabilities and, in general, a good agreement with available data is obtained. The calculated spectra display fingerprints of a second-order shape phase transition that can approximately be described by analytic solutions corresponding to the E(5) dynamical symmetry.