Novel structure for magnetic rotation bands in 60Ni

P.W Zhao,S.Q Zhang,J Peng,H.Z Liang,P Ring,J Meng

doi:10.1016/j.physletb.2011.03.068

Abstract

The self-consistent tilted axis cranking relativistic mean-field theory based on a point-coupling interaction has been established and applied to investigate systematically the newly observed shears bands in 60Ni. The tilted angles, deformation parameters, energy spectra, and reduced M1 and E2 transition probabilities have been studied in a fully microscopic and self-consistent way for various configurations and rotational frequencies. It is found the competition between the configurations and the transitions from the magnetic to the electric rotations have to be considered in order to reproduce the energy spectra as well as the band crossing phenomena. The tendency of the experimental electromagnetic transition ratios B(M1)/B(E2) is in a good agreement with the data, in particular, the B(M1) values decrease with increasing spin as expected for the shears mechanism, whose characteristics are discussed in detail by investigating the various contributions to the total angular momentum as well.

Highlights

The study of bands with high angular momenta has been at the forefront of nuclear structure physics for several decades
relativistic mean-field (RMF) models based on point-coupling interactions (RMFPC) [25, 26, 27] have attracted more and more attention owing to the following advantages: firstly, they avoid the use of unphysical mesons with nonlinear self-interactions, especially the fictitious σ-meson, and the solution of the corresponding Klein-Gordon equations; secondly, it is possible to study the role of naturalness [28, 29] in these effective theories for nuclear-structurerelated problems; thirdly, they provide better opportunities to investigate the relationship to nonrelativistic approaches [30]; and because of their numerical simplicity it is relatively easy to study effects beyond mean-field for nuclear low-lying collective excited states [31, 32]
In complete analogy to the successful meson-exchange RMF models [23, 24], a RMF-PC model with a zero-range point-coupling interaction is proposed in Ref. [25], i.e., the σ, ω, and ρ mesons exchange is replaced by the corresponding contact interactions in the scalar-isoscalar, vector-isoscalar, and vector-isovector channels

Summary

Introduction

The study of bands with high angular momenta has been at the forefront of nuclear structure physics for several decades. Focusing on the magnetic rotation bands, in 2008, a completely new computer code for the self-consistent two-dimensional cranking RMF theory has been established [20] It is based on the non-linear mesonexchange models and includes considerable improvements allowing systematic investigations. RMF models based on point-coupling interactions (RMFPC) [25, 26, 27] have attracted more and more attention owing to the following advantages: firstly, they avoid the use of unphysical mesons with nonlinear self-interactions, especially the fictitious σ-meson, and the solution of the corresponding Klein-Gordon equations; secondly, it is possible to study the role of naturalness [28, 29] in these effective theories for nuclear-structurerelated problems; thirdly, they provide better opportunities to investigate the relationship to nonrelativistic approaches [30]; and because of their numerical simplicity it is relatively easy to study effects beyond mean-field for nuclear low-lying collective excited states [31, 32]. The present model will be applied for a systematic investigation of the shears bands in 60Ni with the newly proposed parametrization PC-PK1 [27]

Theoretical framework

Numerical details

Results and discussion

MeV Config3*

Summary