Shape coexistence and the role of axial asymmetry in $^{72}$Ge

TL;DR

This study investigates the complex shape coexistence and axial asymmetry in $^{72}$Ge through advanced Coulomb excitation experiments, revealing evidence for triaxiality and providing insights into its unusual nuclear structure.

Contribution

It presents the first comprehensive experimental analysis of shape coexistence and triaxiality in $^{72}$Ge using model-independent shape invariants and mixing models.

Findings

Evidence for triaxiality in $^{72}$Ge

Shape coexistence confirmed through shape invariants

Significant progress in understanding $^{72}$Ge's structure

Abstract

The quadrupole collectivity of low-lying states and the anomalous behavior of the $0^+_2$ and $2^+_3$ levels in $^{72}$Ge are investigated via projectile multi-step Coulomb excitation with GRETINA and CHICO-2. A total of forty six $E2$ and $M1$ matrix elements connecting fourteen low-lying levels were determined using the least-squares search code, gosia. Evidence for triaxiality and shape coexistence, based on the model-independent shape invariants deduced from the Kumar-Cline sum rule, is presented. These are interpreted using a simple two-state mixing model as well as multistate mixing calculations carried out within the framework of the triaxial rotor model. The results represent a significant milestone towards the understanding of the unusual structure of this nucleus.