Collective band structures in the gamma -soft nucleus 135Nd.

Abstract

The low-lying band structure of $^{135}\mathrm{Nd}$ has been extended to higher spins using the $^{112}\mathrm{Cd}$${(}^{27}$Al,p3n\ensuremath{\gamma}${)}^{135}$Nd and $^{116}\mathrm{Sn}$${(}^{24}$Mg,2p3n\ensuremath{\gamma}${)}^{135}$Nd reactions. Two distinct high-spin structures have been identified. The \ensuremath{\Delta}J=1 band built on the \ensuremath{\nu}${h}_{11/2}$${[514](9/2)}^{\mathrm{\ensuremath{-}}}$ ground state was observed to have a band crossing at ${J}^{\ensuremath{\pi}}$${=(25/2)}^{\mathrm{\ensuremath{-}}}$. 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 \ensuremath{\Delta}J=1 band structure with no signature splitting was observed to be built on a ${J}^{\ensuremath{\pi}}$${=(17/2)}^{(+)}$ state at 1954 keV. Values for the ratios of reduced transition rates B(M1; I \ensuremath{\rightarrow}I-1)/B(E2; I\ensuremath{\rightarrow}I-1) and B(M1; I\ensuremath{\rightarrow}I-1)/B(E2; I\ensuremath{\rightarrow}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 \ensuremath{\Delta}J=1 band, which is thought to be based on a \ensuremath{\nu}${h}_{11/2}$\ensuremath{\bigotimes}\ensuremath{\pi}${h}_{11/2}$\ensuremath{\bigotimes}\ensuremath{\pi}${g}_{7/2}$ three-quasiparticle configuration.