Rotational band structures in 171,172W: Aspects on signature partnership at high spin

The recently observed two and four-quasiparticle high-spin rotational bands in the odd-odd nuclei 166,168,170,172Re 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 166Re (Li et al., 2015) [8] should be both increased by 2ħ to get in consistent with the systematics of the experimental and calculated moments of inertia for the same configurations in 168,170,172Re. The variations of the backbendings/upbendings with increasing neutron number in these nuclei are investigated. The level crossing mechanism is well understood by analyzing 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] (h9/2) orbital on the level crossing in 172Re is also discussed.