Half-lives of isomeric levels of 87mSr, 111mCd, 113mIn and 115mIn activated by 60Co γ-ray irradiation

Isomers having half-lives of a few hours have been photoactivated by 60Co γ-ray irradiation. The γ-rays emitted from isomers were measured with a low-background Ge detector. The decay data were analyzed by both least-squares method and maximum likelihood method and the suitability of the latter method is discussed. The obtained half-lives are: 87mSr: 2.811 ± 0.027 h, 111mCd: 48.30 ± 0.15 min, 113mIn: 1.663 ± 0.011 h and 115mIn: 4.483 ± 0.005 h.