Band structure in 83Rb from lifetime measurements

Excited states of 83Rb, populated in the 76Ge(11B, 4nγ) reaction at a beam energy of 50 MeV, have been studied. The unfavoured signature partner (α=−1/2) of the πg9/2 yrast band is proposed up to an excitation energy of 6669.4 keV and spin (31/2+). Lifetimes have been estimated for three states belonging to the favoured α=+1/2 band. The B(E2) values deduced from these lifetimes indicate a moderate quadrupole deformation of β2=0.20. Theoretical calculations within the framework of the particle-rotor-model suggest that low energy states before the onset of the νg9/2 alignment at a rotational frequency of ∼0.5 MeV are prolate while those above this frequency have an oblate shape. The excited ΔI=1 band has been extended up to 5422.7 keV and spin 25/2−. The B(M1) rates derived from the measured lifetimes decrease with spin. The results are in general agreement with an earlier TAC calculation, suggesting the interpretation of these states as arising from magnetic rotation.