Quadrupole pairing interaction and signature inversion

Abstract

The signature inversion in the πh 11/2 νh 11/2 rotational bands of the odd-odd Cs and La isotopes and the πh 11/2 νi 13/2 bands of the odd-odd Tb, Ho and Tm nuclei is investigated using pairing and deformation self-consistent mean-field calculations. The model can rather satisfactorily account for the anomalous signature splitting provided that spin assignments in some of the bands are revised. Our calculations show that signature inversion can appear already at axially symmetric shapes. It is found that this is due to the contribution of the (λµ) = (22) component of the quadrupole-pairing interaction to the mean-field potential.

Spectroscopy ofHo144using recoil-isomer tagging

“…Theoretically, the α = 1 signature is the energetically favored signature for a πh 11/2 ⊗ νh 11/2 quasiparticle configuration [27]. In this work, the favored signature partner band was observed to be higher in energy than the unfavored α = 0 band, indicating that Bands 1a and 1b are signature inverted.…”

“…It has been attributed theoretically to triaxiality [29] but has since also been shown to be consistent with axially symmetric nuclear shapes [30]. Signature inversion is now often described in terms of a residual proton-neutron interaction [27,31].…”

Multi-quasiparticle high-K isomeric states in deformed nuclei

“…The quadrupole pairing can also be included [17] but its effect on the excitation energies of multi-quasiparticle states is small [18]. Due to nucleon pair(s) broken in multi-quasiparticle states, the pairing correlation is reduced remarkably in high-K states.…”

“…The β 4 deformation is determined by minimizing the energy at each (β 2 , γ) point. The γ deformation plays an important role in the description of nuclear collective rotation [17,19,20] and high-K excitations [21][22][23][24][25]. The γ deformation results in K-mixing (K is a conserved number for axially symmetric shape [26][27][28]).…”

Superdeformed multi-quasiparticle high-Kstates and possible isomers in Pb and Po isotopes

“…To see the relative energies between the multi-qp bandheads and the yrast SD states, we have performed pairingdeformation self-consistent total Routhian surface (TRS) calculations for the collective SD bands [21,26]. Quadrupole pairing in doubly stretched coordinate space [27] has a negligible effect on energies, but it is included (with the strength determined by restoring the local Galilean invariance) because it has an important influence on collective angular momenta [28,29].…”