Collective band structures in theγ-soft nucleusNd135

Abstract

The low-lying band structure of ${}_{}{}^{135}{}_{}{}^{}\mathrm{Nd}$ has been extended to higher spins using the ${}_{}{}^{112}{}_{}{}^{}\mathrm{Cd}$ ${(}^{27}$Al,p3nγ${)}^{135}$Nd and ${}_{}{}^{116}{}_{}{}^{}\mathrm{Sn}$ ${(}^{24}$Mg,2p3nγ${)}^{135}$Nd reactions. Two distinct high-spin structures have been identified. The ΔJ=1 band built on the ν$h_{11/2}$ ${\left[514\right]\mathrm{}(9/2)\mathrm{}}^{\mathrm{-}}$ ground state was observed to have a band crossing at $J^{\pi }$ ${=(25/2)\mathrm{}}^{\mathrm{-}}$. This band crossing is associated with a loss of the moderate signature splitting found below the backbend. Cranked-shell model calculations suggest that this structure involves the alignment of a pair of $h_{11/2}$ protons and that the loss of signature splitting can be attributed to a shape change from a triaxial shape at low spins to a prolate axial shape above the backbend. A second ΔJ=1 band structure with no signature splitting was observed to be built on a $J^{\pi }$ ${=(17/2)\mathrm{}}^{\mathrm{}(+)\mathrm{}}$ state at 1954 keV. Values for the ratios of reduced transition rates B(M1; I →I-1)/B(E2; I→I-1) and B(M1; I→I-1)/B(E2; I→I-2) have been extracted from transitions in the two bands. Comparisons with theoretical predictions helped in the identification of the structure of the second ΔJ=1 band, which is thought to be based on a ν$h_{11/2}$⊗π$h_{11/2}$⊗π$g_{7/2}$ three-quasiparticle configuration.