Observation ofγvibrations and alignments built on non-ground-state configurations inDy156

Abstract

The exact nature of the lowest K π =2 + rotational bands in all deformed nuclei remains obscure. Traditionally they are assumed to be collective vibrations of the nuclear shape in the γ degree of freedom perpendicular to the nuclear symmetry axis. Very few such γ-bands have been traced past the usual back-bending rotational alignments of high-j nucleons. We have investigated the structure of positive-parity bands in the N=90 nucleus 156 Dy, using the 148 Nd(

Quasiparticle and γ -band structures in Dy156

“…The CSM gives two even-spin (ABEF and ABef) and one odd-spin (AC) bands between the s-and the g-bands, where Ref. [6] suggests the experimental location of the two signatures of the γ-band on top of the s-band. The close neighborhood may cause fragmentation of the collective strength among these two-quasiparticle (relative to AB) excitations.…”

“…4, have interesting structures with dominant component from (3, 2n), which is the γ-band based on the twoquasineutron configuration. been proposed in the experimental work [6]. The component (3, 2n), which is γ-band built on the two-neutron aligned configuration, is quite dominant in the wavefunctions of the band structures labelled as Band 17 and Band 20.…”

“…2 and 3. The bands are labelled as in the experimental work [6]. The association between the calculated and experimental bands is discussed below.…”

“…In a more recent experimental study [6], the high-spin band structures in 156 Dy have been populated. The most interesting aspect of this investigation is the observation of the γ-band based on the ground-state up to highest angular-momentum, I=32 observed so far.…”

“…The recent experimental study of 156 Dy [6] provided evidence for the existence of a γ-band based on the ground-state band up to very high spins and a second γ-band, which is proposed to be built on the s-configuration, which contains two rotational aligned i 13/2 quasineutrons. The purpose of the present work is to investigate the conjectured γ-bands, based on the quasiparticle excitations, using the TPSM approach as well as in the framework of the traditional approaches based on the rotating mean-field.…”