Lifetime measurement of the low lying yrast states in 189Pt

TL;DR

This paper reports precise lifetime measurements of low-lying states in 189Pt using recoil distance Doppler-shift, revealing shape evolution effects in the nucleus's yrast band.

Contribution

It provides new lifetime data for 189Pt's yrast states, highlighting shape-driving effects of quasi-neutrons in this isotope.

Findings

Large quadrupole transition (Qt) value for 17/2+ state

Qt value decreases rapidly with increasing spin

Shape driving effect from quasi-neutron i13/2 orbital

Abstract

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.