Lifetime measurement in picoseconds for the excited states of 129Cs

Abstract

The high-spin states of 129Cs were populated using the fusion-evaporation reaction 124Sn(11B, 6n)129Cs. We have studied the nuclear structure properties – signature splitting and reduced transition probabilities (B(E2)) – of many excited states in 129Cs. Lifetimes in picoseconds were measured using the Doppler Shift Attenuation Method (DSAM). We employed two gating procedures, Gating on transition above (GTA) and Gating on transition below (GTB), to obtain the experimental results consistently. We carefully analyzed the data by incorporating the effects related to nuclear reaction, e.g., change in the velocity and cross section of residues when moving in a medium. Theoretical investigations were carried out for two yrast bands – a positive-parity based on πg7/2, and another negative-parity based on πh11/2 – using the single quasi-particle rotor model (PRM). For both bands, we found the same deformation parameter values ϵ≃0.14, |γ|=18∘ (Lund convention) by simultaneously matching the experimental and theoretical results for the signature splitting and B(E2) values. Most of our results are new and reasonably well understood theoretically.