Microscopic description of octupole collective excitations near $N=56$ and $N=88$

TL;DR

This study uses nuclear density functional theory to analyze octupole deformations and collective excitations in various isotopes, revealing regions with enhanced octupole correlations and shape phase transitions near specific neutron and proton numbers.

Contribution

It provides a microscopic description of octupole excitations across different isotopes using constrained mean-field calculations and collective Hamiltonian modeling.

Findings

Octupole-deformed states are found in Ba and Ce isotopes near N=56 and 88.

Enhanced octupole correlations are observed around N≈Z≈56 and Z≈88.

Signatures of octupole shape phase transition are identified near N=56 and 88.

Abstract

Octupole deformations and related collective excitations are analyzed using the framework of nuclear density functional theory. Axially-symmetric quadrupole-octupole constrained self-consistent mean-field (SCMF) calculations with a choice of universal energy density functional and a pairing interaction are performed for Xe, Ba, and Ce isotopes from proton-rich to neutron-rich regions, and neutron-rich Se, Kr, and Sr isotopes, in which enhanced octupole correlations are expected to occur. Low-energy positive- and negative-parity spectra and transition strengths are computed by solving the quadrupole-octupole collective Hamiltonian, with the inertia parameters and collective potential determined by the constrained SCMF calculations. Octupole-deformed equilibrium states are found in the potential energy surfaces of the Ba and Ce isotopes with $N\approx 56$ and 88. The evolution of spectroscopic properties indicates enhanced octupole correlations in the regions corresponding to $N\approx Z\approx 56$, $Z\approx 88$ and $Z\approx 56$, and $N\approx 56$ and $Z\approx 34$. The average $\beta_{30}$ deformation parameter and its fluctuation exhibit signatures of octupole shape phase transition around $N=56$ and 88.