Characteristics of collectivity along the yrast line in even-even tungsten isotopes

Abstract

The collective nature of high-spin yrast states in even-even $^{160\ensuremath{-}190}\mathrm{W}$ isotopes was systematically investigated by means of pairing self-consistent Woods-Saxon-Strutinsky calculations using the total Routhian surface approach in $({\ensuremath{\beta}}_{2},\ensuremath{\gamma},{\ensuremath{\beta}}_{4})$ deformation space. The calculated ground-state deformations are consistent with previous calculations and available experimental data. The deformation energy curves are presented to show the shape and softness evolutions, in particular in the triaxial direction. The backbending or upbending behavior in moment of inertia is attributed to band crossing. It is found that the neutron rotation alignment is preferred for most of the W isotopes (e.g., in $^{164\ensuremath{-}180}\mathrm{W}$), while in other nuclei the competition between the neutron and proton alignments may occur, even the proton alignment is favored in the very neutron-deficient nucleus $^{160}\mathrm{W}$. In addition, the evolution and transition between vibrational and rotational collective modes along the yrast line are investigated on the basis of the new centipedelike E-GOS (E-Gamma Over Spin) curves introduced by us, which to some extent explains the existing differences (e.g., in the moment of inertia) between theory and experiment.