Possible Presence and Properties of Multi Chiral Pair-Bands in Odd-Odd Nuclei with the Same Intrinsic Configuration

TL;DR

This study uses a particle-rotor model to explore the potential existence and properties of multi chiral pair-bands in odd-odd nuclei, focusing on their energy levels, decay modes, and conditions for their formation.

Contribution

It introduces a simple particle-rotor model to identify conditions for multi chiral pair-bands and analyzes their decay properties and energy differences in odd-odd nuclei.

Findings

Chiral pair-bands are favored within a specific gamma range (25°-35°).

Intraband M1/E2 decay dominates over interband decay near band-heads.

No stable chiral pair-bands with constant energy difference of hundreds of keV were found.

Abstract

Applying a relatively simple particle-rotor model to odd-odd nuclei, possible presence of multi chiral pair-bands is looked for, where chiral pair-bands are defined not only by near-degeneracy of the levels of two bands but also by almost the same expectation values of squared components of three angular-momenta that define chirality. In the angular-momentum region where two pairs of chiral pair-bands are obtained the possible interband M1/E2 decay from the second-lowest chiral pair-bands to the lowest chiral pair-bands is studied, with the intention of finding how to experimentally identify the multi chiral pair-bands. It is found that up till almost band-head the intraband M1/E2 decay within the second chiral pair-bands is preferred rather than the interband M1/E2 decay to the lowest chiral pair-bands, though the decay possibility depends on the ratio of actual decay energies. It is also found that chiral pair-bands in our model and definition are hardly obtained for $\gamma$ values outside the range $25^{\circ} < \gamma < 35^{\circ}$, although either a near-degeneracy or a constant energy-difference of several hundreds keV between the two levels for a given angular-momentum $I$ in "a pair bands" is sometimes obtained in some limited region of $I$. In the present model calculations the energy difference between chiral pair-bands is always one or two orders of magnitude smaller than a few hundreds keV, and no chiral pair-bands are obtained, which have an almost constant energy difference of the order of a few hundreds keV in a reasonable range of $I$.