Lifetimes of High Spin States in an Odd-Proton Nucleus 129Cs

Abstract

Lifetimes of high spin states in 129Cs are measured using the Doppler shift attenuation method. The high spin states of 129Cs are populated following the fusion evaporation reaction 124Sn(11B, 6n)129Cs at a beam energy of 65 MeV. The reduced transition probabilities B(E2) and the transition quadrupole moments Qt in the negative- and positive-parity bands are deduced. The experimental results indicate that the Qt values of the negative parity band are smaller than those of the positive parity bands, probably due to different γ-deformation driving effects of different proton orbitals. The Qt values exhibit a considerable increase near the band crossing region in these bands. This behavior demonstrates that nuclear shape changing results from the neutron or proton alignments. The signature splitting of the πh11/2 and πg7/2 bands shows the opposite changing trend after backbending due to the h11/2 neutron and h11/2 proton alignments, respectively.