Lifetime Measurement of the Low Lying Yrast States in ¹⁸⁹Pt

High-spin states in ¹⁸⁹Pt are populated through the heavy-ion fusion-evaporation reaction¹⁷⁶Yb (¹⁸O, 5n)¹⁸⁹Pt at 87 MeV beam energy. An array consisting of 13 HPGe detectors is used in conjunction with the plunger device in CIAE. The lifetimes of two levels in the yrast band are determined by using the recoil distance Doppler shift method. The transition quadrupole moments Q_t are extracted. The results show that the 17/2⁺ state has a much larger Q_t value than that of the ground state, whereas the value deceases quickly with spin increasing. This may contribute to the shape driving effect of the quasi-neutron from the em_13/2 orbital.