Side-feeding times and level lifetimes measured in the reaction 54Fe( 32S, 3p) 83Y

Abstract

We have performed recoil-distance and Doppler-shift-attenuation lifetime measurements in the reaction 54Fe( 32S, 3p) 83Y at 103–107 MeV beam energy. By analyzing the Doppler-broadened line shapes of the 964 keV 21 2 + → 17 2 + yrast transition in coincidence with feeding and depopulating transitions, the average side-feeding time and lifetime of this state have been deduced as τ F = 0.6(2) ps and τ = 0.62(10) ps, respectively. A similar analysis of the 811 keV 17 2 +→ 13 2 + transition gave values of τ F = 0.65(25) ps and τ = 1.5(2) ps, respectively for the 17 2 + yrast state. Feeding times of the higher transitions in the positive-parity yrast band have been estimated from their Dopplerbroadened lineshapes measured in coincidence with depopulating transitions only. The feeding times are compared with the results of Monte Carlo calculations of the time development of the continuum γ-ray flux, and a damping width of 2–3 MeV has been deduced. The measured level lifetimes support the regular band structures with the deformation β 2 = 0.33 previously inferred from the transition energies.