High-Spin Doublet Band Structures in odd-odd $^{194-200}$Tl isotopes

TL;DR

This paper extends the triaxial projected shell model to study high-spin doublet band structures in odd-odd $^{194-200}$Tl isotopes, exploring chiral symmetry breaking and providing theoretical insights into observed phenomena.

Contribution

It introduces a generalized TPSM approach for odd-odd nuclei, enabling analysis of doublet bands and chiral symmetry in $^{194-200}$Tl isotopes beyond the band crossing region.

Findings

Small energy differences in doublet bands support chiral symmetry.

Calculated transition probabilities show deviations from ideal chiral symmetry.

The model successfully explains observed high-spin band structures.

Abstract

The basis space in the triaxial projected shell model (TPSM) approach is generalized for odd-odd nuclei to include two-neutron and two-proton configurations on the basic one-neutron coupled to one-proton quasiparticle state. The generalization allows to investigate odd-odd nuclei beyond the band crossing region and as a first application of this development, high-spin band structures recently observed in odd-odd $^{194-200}$Tl isotopes are investigated. In some of these isotopes, the doublet band structures observed after the band crossing have been conjectured to arise from the spontaneous breaking of the chiral symmetry. The driving configuration of the chiral symmetry in these odd-odd isotopes is one-proton and three-neutrons rather than the basic one-proton and one-neutron as already observed in many other nuclei. It is demonstrated using the TPSM approach that energy differences of the doublet bands in $^{194}$Tl and $^{198}$Tl are, indeed, small. However, the differences in the calculated transition probabilities are somewhat larger than what is expected in the chiral symmetry limit. Experimental data on the transition probabilities is needed to shed light on the chiral nature of the doublet bands.