Microscopic origin of shape coexistence in the N=90, Z=64 region

TL;DR

This paper provides a microscopic explanation for shape coexistence in N=90, Z=64 nuclei, attributing it to proton-induced neutron excitations across magic numbers that lead to deformation and phase transitions.

Contribution

It introduces a covariant density functional theory-based model explaining shape coexistence via proton-driven neutron excitations across magic numbers.

Findings

Shape coexistence linked to proton-induced neutron excitations.

Onset of deformation associated with occupation of intruder orbitals.

Similar effects observed in N=60, Z=40 region.

Abstract

A microscopic explanation of the nature of shape coexistence in the N=90, Z=64 region is suggested, based on calculations of single particle energies through standard covariant density functional theory. It is suggested that shape coexistence in the N=90 region is caused by the protons, which create neutron particle-hole (p-h) excitations across the N=112 3-dimensional isotropic harmonic oscillator (3D-HO) magic number, signaling the start of the occupation of the 1i13/2 intruder orbital, which triggers stronger proton-neutron interaction, causing the onset of the deformation and resulting in the shape/phase transition from spherical to deformed nuclei described by the X(5) critical point symmetry. A similar effect is seen in the N=60, Z=40 region, in which p-h excitations across the N=70 3D-HO magic number occur, signaling the start of the occupation of the 1h11/2 intruder orbital.