Robust Regularity in \gamma-Soft Nuclei and its Microscopic Realization

TL;DR

This paper investigates b3-softness in nuclei using energy density functionals and the IBM-2 model, revealing that real nuclei exhibit properties intermediate between rigid-triaxial and b3-unstable limits, guiding optimal model selection.

Contribution

It provides a microscopic realization of b3-soft nuclei, bridging the gap between two classical geometrical models through energy density functional mapping.

Findings

Real nuclei are intermediate between rigid-triaxial and b3-unstable limits.

Microscopic description aligns with an intermediate b3-softness.

Optimal IBM Hamiltonian for b3-soft nuclei is identified.

Abstract

\gamma-softness in atomic nuclei is investigated in the framework of energy density functionals. By mapping constrained microscopic energy surfaces for a set of representative non-axial medium-heavy and heavy nuclei to a Hamiltonian of the proton-neutron interacting boson model (IBM-2) containing up to three-body interactions, low-lying collective spectra and transition rates are calculated. Observables are analyzed that distinguish between the two limiting geometrical pictures of non-axial nuclei: the rigid-triaxial rotor and the \gamma-unstable rotor. It is shown that neither of these pictures is realized in actual nuclei, and that a microscopic description leads to results that are almost exactly in between the two geometrical limits. This finding points to the optimal choice of the IBM Hamiltonian for \gamma-soft nuclei.