Gamma-Gamma Directional Correlation in the Decay of 168Tm

Abstract

Time-integral and time-differential gamma-gamma directional correlation measurements were performed for cascades in 168 Er populated from the decay of 168 Tm (90d.). The mixing parameters of most of the intense gamma-rays have been determined more precisely than ever. Some ambiguities concerning to the directional correlation coefficients of the 447–198 keV and 447–830 keV cascades were well removed. The directional correlation coefficients of these cascades were determined as A 22 =0.009 ±0.003 and -0.067 ±0.008, respectively, and A 44 ≈0 for both. The mixing parameters of the 198-, 447- and 830-keV gamma-rays were determined as δ(198)=0.13 ±0.02, δ(447)=0.09 ±0.01 and δ(830)=0.05 ±0.03, respectively. The transition probabilities of the gamma-rays deexciting the 1094-keV level are deduced on the basis of this work.