Octupole deformation and Ra puzzle in reflection asymmetric covariant density functional theory

TL;DR

This paper uses reflection asymmetric covariant density functional theory to explain the Ra puzzle, showing that octupole deformation causes the anomalous proton-neutron interaction enhancement in Ra isotopes around N=135.

Contribution

It introduces a reflection asymmetric CDFT approach based on a two-center harmonic-oscillator basis to analyze octupole deformation in Ra isotopes.

Findings

Octupole deformation explains the Ra puzzle.

The model reproduces residual proton-neutron interactions.

Shape evolution is characterized in potential energy surfaces.

Abstract

Reflection asymmetric covariant density functional theory(CDFT) based on the point-coupling interaction is established on a two-center harmonic-oscillator basis and applied to investigate the Ra puzzle, i.e., the anomalous enhancement of the residual proton-neutron interactions for Ra isotopes around N=135. The octupole deformation and shape evolution in the Ra and Rn isotopes are examined in the potential energy surfaces in(beta2, beta3) plane by the constrained reflection asymmetric calculations. The residual proton-neutron interactions extracted from the double difference of the binding energies for Ra isotopes are compared with the data as well as the axial and the triaxial calculations. It is found that the octupole deformation is responsible for the Ra puzzle in the microscopic CDFT.