General properties of the πh9/2[541]1/2 − configuration and level scheme of 165Tm

Abstract

165Tm has been studied through the reactions 150Nd( 19F, 4n), E beam=85 MeV and 154Sm ( 15N, 4n), E beam=70 MeV. The level scheme has been extended to spin 71/2 −ℏ, and four new bands have been added. Two are assigned to the K=17/2, three-quasiparticle configurations, π[523]7/2 −⊗ ν[642]5/2 +⊗ ν[523]5/2 − and π[404]7/2 +⊗ ν[642]5/2 +⊗ ν[523]5/2 −, and the remaining two are assigned to γ-vibrations coupled to an h 9/2 proton. Lifetimes of high-spin states in the [541]1/2 − and [411]1/2 + bands have been measured using DSAM techniques, allowing transition quadrupole moments to be deduced. Furthermore, crossings between the [541]1/2 − and [523]7/2 − bands and between the [411]1/2 + and [404]7/2 + bands are analysed with a band-mixing calculation to obtain the quadrupole moments of the [523]7/2 − and [404]7/2 + bands. While the [523]7/2 −, [411]1/2 + and [404]7/2 + bands all have similar deformations, the [541]1/2 − band has a quadrupole moment approximately 15% larger. The relative deformations are in good agreement with diabatic potential energy surface calculations performed using the code “Ultimate Cranker”. The experimental crossing frequency, due to the alignment of i 13/2 neutrons, is found to be delayed in the [541]1/2 − band compared to the other bands. This is a universal feature in the rare-earth region, and extensive systematic Cranked Shell Model calculations have been performed to predict deformations and crossing frequencies for nuclei in the region. The model is unable to reproduce the full delay in crossing frequency, confirming that deformation alone is not responsible for the shift.