Simultaneous quadrupole and octupole shape phase transitions in Thorium

TL;DR

This paper investigates the simultaneous evolution of quadrupole and octupole shapes in Thorium isotopes, revealing a double quantum shape phase transition driven by neutron number changes, using nuclear Density Functional Theory.

Contribution

It provides the first microscopic analysis of simultaneous quadrupole and octupole shape phase transitions in Thorium isotopes with detailed theoretical modeling.

Findings

Identification of a double phase transition in Th isotopes.

$^{224}$Th is near the critical point of the transition.

Evolution of single-nucleon orbitals explains the phenomenon.

Abstract

The evolution of quadrupole and octupole shapes in Th isotopes is studied in the framework of nuclear Density Functional Theory. Constrained energy maps and observables calculated with microscopic collective Hamiltonians indicate the occurrence of a simultaneous quantum shape phase transition between spherical and quadrupole-deformed prolate shapes, and between non-octupole and octupole-deformed shapes, as functions of the neutron number. The nucleus $^{224}$Th is closest to the critical point of a double phase transition. A microscopic mechanism of this phenomenon is discussed in terms of the evolution of single-nucleon orbitals with deformation.