Systematic investigation of the high-spin structures in the odd-odd nuclei $^{166, 168, 170, 172}$Re by a particle-number conserving method

TL;DR

This paper uses a particle-number conserving cranked shell model to analyze high-spin structures in odd-odd Re isotopes, confirming spin assignments and exploring the effects of neutron number and orbital interactions on rotational behaviors.

Contribution

It provides a systematic investigation of high-spin rotational bands in Re isotopes using a particle-number conserving approach, clarifying spin assignments and level crossing mechanisms.

Findings

Reproduces experimental moments of inertia and alignments.

Suggests increasing bandhead spins in $^{166}$Re by 2ħ for consistency.

Analyzes the variation of backbendings/upbendings with neutron number.

Abstract

The recently observed two and four-quasiparticle high-spin rotational bands in the odd-odd nuclei $^{166, 168, 170, 172}$Re are investigated using the cranked shell model with pairing correlations treated by a particle-number conserving method. The experimental moments of inertia and alignments can be reproduced well by the present calculation if appropriate bandhead spins and configurations are assigned for these bands, which in turn confirms their spin and configuration assignments. It is found that the bandhead spins of those two rotational bands observed in $^{166}$Re~[Li {\it et al.}, Phys. Rev. C 92 014310 (2015)] should be both increased by $2\hbar$ to get in consistent with the systematics of the experimental and calculated moments of inertia for the same configurations in $^{168, 170, 172}$Re. The variations of the backbendings/upbendings with increasing neutron number in these nuclei are investigated. The level crossing mechanism is well understood by analysing the variations of the occupation probabilities of the single-particle states close to the Fermi surface and their contributions to the angular momentum alignment with rotational frequency. In addition, the influence of the deformation driving effects of the proton $1/2^-[541]$ ($h_{9/2}$) orbtial on the level crossing in $^{172}$Re is also discussed.