Lifetime measurement of the low lying yrast states in 189Pt

Lifetimes of the positive-parity yrast band in 189Pt were measured using the recoil distance Doppler-shift method. A HPGe detector array consisting of 13 detectors was used in conjunction with the plunger device in CIAE. Excited states of 189Pt were populated by the 176Yb (18O, 5n) 189Pt fusion-evaporation reaction at a beam energy 87 MeV. The lifetimes of two levels belonging to the yrast band are measured. The results show that the 17/2+ state in the yrast band has large Qt value, but it deceases quickly with spin increasing. It may be contributed from the shape driving effect of the quasi-neutron from the i13/2 oribital.