MASS ASSIGNMENT OF THE 1.8 HOUR YTTERBIUM ACTIVITY

The rate of growth of Lu 177 into neutron-irradiated ytterbium has been measured by radioassay of lutetium fractions separated by ion-exchange techniques. Such measurements show the parent of Lu 177 to be the 1.8 hour Yb; this latter nuclide is therefore Yb 177 . Confirmatory values of 3.71 ± 0.04 hours and 6.75 ± 0.05 days have been obtained for the half-lives of Lu 176m and Lu 177 .