Systematic Investigation Of The High-spin Structures In The Odd-odd Nuclei^{166,168,170,172}Re By A Particle-number Conserving Method

Since the 1950s,the rotation of nucleus has been one of the important research fields of nuclear structures.The high-spin structures of the rare-earth nuclei have drawn a lot of attentions owing to the existence of various exotic excitation modes,such as backbending,signature inversion,band termination,superdeformation,wobbling mode,etc.Compared to even-even and odd-A nuclei,the odd-odd nuclei often show a broader variety of nuclear structure phenomena.In addition,due to the unpaired valence quasiproton and the unpaired valence quasineutron in the odd-odd nuclei,the coupling between them makes the properties of odd-odd nuclei more complicated.This also provides a further test to the various theoretical nuclear models which describe the rotation of the nucleus.Pairing correlations play a very important role in the nuclear rotational properties.The traditional methods which are used to treat the pairing correlations are Bardeen-Cooper-Schrieffer or Hartree-Fock-Bogoliubov approximations.In these approaches,the particle-number is not totally conserved and the Pauli blocking effects are not taken into account exactly.Therefore,non-physical pairing collapse often occurs in the study of high-spin states of nucleus and high-K isomers.To overcome this difficulty,particle-number conserving method was proposed by Prof.Jin-Yan Zeng et al.,which was used to deal with the pairing correlations.In the particle-number conserving method,the pairing Hamiltonian is diagonalized directly in a properly truncated Fock space.Therefore,the particle-number is strictly conserved and the Pauli blocking effects are taken into account exactly.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 the 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.However,it is found that the bandhead spins of those two rotational bands observed in 166Re[Li et al.,Phys.Rev.C 92014310(2015)]should both increase by 2h to get in consistent with the systematics of the experimental and calculated moments of inertia for the same configuration 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 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](h9/2)orbtial on the level crossing in 172Re is also discussed.