Anomalous low-energy $E2$-related behavior in triaxial nuclei

TL;DR

This paper investigates unusual low-energy E2 transition behaviors in triaxial nuclei using the interacting boson model and SU(3) algebra, explaining experimental anomalies in neutron-deficient nuclei.

Contribution

It introduces an algebraic approach within the interacting boson model to explain anomalous E2 behaviors in triaxial nuclei, highlighting finite-N effects.

Findings

Identifies a transition rate ratio less than 1.0 in certain nuclei.

Shows an excitation energy ratio greater than 2.0 in these nuclei.

Explains anomalies in neutron-deficient nuclei like $^{172}$Pt and $^{168}$Os.

Abstract

The anomalous low-energy $E2$-related behavior of a triaxially-deformed nucleus bas been identified and analyzed based on the SU(3) algebraic theory within the framework of the interacting boson model. The results show striking features that include a $B(E2;4_1^+\rightarrow2_1^+)/B(2_1^+\rightarrow0_1^+)<1.0$ transition rate ratio and a $E(4_1^+)/E(2_1^+)>2.0$ excitation energy ratio that can be tracked back to a finite-$N$ effect, which in a large-$N$ limit of the theory yields normal results for a stable $\gamma$-deformation. This description is shown to be able to explain observed $E2$ anomalous phenomenon in neutron-deficient nuclei such as $^{172}$Pt and $^{168}$Os, and in so doing yields a deeper understanding of the physical features of a soft triaxially-deformed nucleus.