Absolute E1 transition probabilities in the deformed nuclei Yb 177 and Hf 179

Abstract

The absolute E1 transition probabilities have been measured for two 7 2 −(514) levels populated from the short-lived isomers Yb 177m(6.4 s) and Hf 179m(18.6 s), a delayed coincidence set-up being used for the purpose. This gave a half life of T 1 2 = 4.48±0.08 ns for the 104 keV level in Yb 177 and T 1 2 = 1.86±0.05 ns for the 217 keV level in Hf 179. The result has been compared with the calculations made by Nilsson. The effect of the pairing correlation has also been taken into account. An agreement with the experimental values to within a factor of three is obtained. An extrapolated estimate of the half life for the 408.9 keV 7 2 −(514) level in W 181 gives 3·10 −11 s.