Octupole deformation for Ba isotopes in a reflection-asymmetric relativistic mean-field approach

TL;DR

This study investigates octupole deformation in Ba isotopes using a reflection-asymmetric relativistic mean-field approach, revealing shape transitions and specific nuclei with significant octupole deformation.

Contribution

It introduces a detailed analysis of octupole deformation across Ba isotopes within a relativistic mean-field framework, highlighting the role of specific single-particle level pairs.

Findings

$^{142}$Ba is near spherical, $^{156}$Ba is well quadrupole-deformed.

$^{144-154}$Ba exhibit octupole deformation, especially $^{148,150}$Ba.

Energy gaps and single-particle level analysis support octupole deformation mechanisms.

Abstract

The potential energy surfaces of even-even $^{142-156}$Ba are investigated in the constrained reflection-asymmetric relativistic mean-field approach with parameter set PK1. It is shown that for the ground states, $^{142}$Ba is near spherical,$^{156}$Ba well quadrupole-deformed, and in between $^{144-154}$Ba octupole deformed. In particular, the nuclei $^{148,150}$Ba with $N=92,94$ have the largest octupole deformations. By including the octupole degree of freedom, energy gaps $N=88$, $N=94$ and $Z=56$ near Fermi surfaces for the single-particle levels in $^{148}$Ba with $\beta_2\sim 0.26$ and $\beta_3\sim 0.17$ are found. Furthermore, the performance of the octupole deformation driving pairs ($\nu 2f_{7/2}$, $\nu 1i_{13/2}$) and ($\pi 2d_{5/2}$, $\pi 1h_{11/2}$) is demonstrated by analyzing the single-particle levels near Fermi surfaces in $^{148}$Ba.