Prolate-oblate shape transitions and O(6) symmetry in even-even nuclei: A theoretical overview

TL;DR

This paper reviews theoretical predictions and experimental evidence of prolate-oblate shape transitions in nuclei, highlighting the role of O(6) symmetry in the Interacting Boson Model and related symmetries across the nuclear chart.

Contribution

It provides a comprehensive overview of shape transition predictions using various symmetries and confirms their consistency with experimental data and mean field calculations.

Findings

Prolate-oblate transitions predicted analytically in IBM with O(6) symmetry.

Parameter-independent predictions confirmed by multiple models.

Experimental data supports regions of O(6) symmetry and shape transitions.

Abstract

Prolate to oblate shape transitions have been predicted in an analytic way in the framework of the Interacting Boson Model (IBM), determining O(6) as the symmetry at the critical point. Parameter-independent predictions for prolate to oblate transitions in various regions on the nuclear chart have been made in the framework of the proxy-SU(3) and pseudo-SU(3) symmetries, corroborated by recent non-relativistic and relativistic mean field calculations along series of nuclear isotopes, with parameters fixed throughout, as well as by shell model calculations taking advantage of the quasi-SU(3) symmetry. Experimental evidence for regions of prolate to oblate shape transitions is in agreement with regions in which nuclei bearing the O(6) dynamical symmetry of the IBM have been identified, lying below major shell closures. In addition, gradual oblate to prolate transitions are seen when crossing major nuclear shell closures, in analogy to experimental observations in alkali clusters.