Microscopic formulation of the interacting boson model for reflection asymmetric nuclei

TL;DR

This paper reviews the microscopic formulation of the interacting boson model for reflection asymmetric nuclei, emphasizing recent advances in understanding octupole shapes and collective excitations through nuclear density functional theory.

Contribution

It introduces a microscopic approach to the interacting boson model using mean-field methods, highlighting shape phase transitions and octupole collectivity in nuclei.

Findings

Stable octupole deformation observed in light actinides.

Shape phase transition involving quadrupole and octupole degrees of freedom.

Enhanced octupole collectivity across a wide mass region.

Abstract

Reflection asymmetric, octupole shapes in nuclei are a prominent aspect of nuclear structure, and have been recurrently studied over the decades. Recent experiments using radioactive-ion beams have provided evidence for stable octupole shapes. A variety of nuclear models have been employed for the related theoretical analyses. We review recent studies on the nuclear octupole shapes and collective excitations within the interacting boson model. A special focus is placed on the microscopic formulation of this model by using the mean-field method that is based on the framework of nuclear density functional theory. As an illustrative example, a stable octupole deformation, and a shape phase transition as a function of nucleon number that involves both quadrupole and octupole degrees of freedom are shown to occur in light actinides. Systematic spectroscopic studies indicate enhancement of the octupole collectivity in a wide mass region. Couplings between the octupole and additional degrees of freedom are incorporated in a microscopic manner in the boson system, and shown to play a crucial role in the description of the related intriguing nuclear structure phenomena such as the shape coexistence.