Lifetime measurements in the yrast band of the gamma-soft nuclei 131 Ce and 133 Pr

Lifetimes of excited states in the yrast band of the gamma-soft nuclei 131 Ce and 133 Pr have been measured using the recoil distance Doppler shift and Doppler shift attenuation methods. The yrast bands in 131 Ce and 133 Pr are based on odd decoupled neutron νh 11/2 high Ω and proton π h 11/2 low Ω orbitals, respectively. The triaxiality parameter extracted from the experimentally deduced values of transition quadrupole moments, within the framework of cranked Hartree–Fock–Bogoliubov (CHFB) and total Routhian surface (TRS) calculatons, is γ ∼ −80 ∘ for the band in 131 Ce at high spins, while for the band in 133 Pr, the value of γ is close to 0 ∘ . This agrees well with the γ shape polarization property of high and low Ω h 11/2 orbitals in these gamma-soft nuclei.