Half-Life Determinations by Direct Decay

Half-lives have been measured by direct decay for 18 radionuclides. The method of least squares was used to obtain the best straight-line fit to the data. The observed half-lives are 87.9 ± 0.3 d for S³⁵, 52.7 ± 0.5 d for Sr⁸⁹, 13.6 ± 0.3 y for Nb^93m, 35.8 ± 0.5 d for Nb⁹⁵, 65.5 ± 0.2 d for Zr⁹⁵, 39.5 ± 0.3 d for Ru¹⁰³, 368.0 ± 1.8 d for Ru¹⁰⁶, 13.6 ± 0.2 y for Cd¹¹³, 76.3 ± 6.6 y for Sn¹²¹, 2.71 ± 0.02 y for Sb¹²⁵, 1.99 ± 0.02 y for Cs¹³⁴, 283.8 ± 0.6 d for Ce¹⁴⁴, 2.60 ± 0.02 y for Pm¹⁴⁷, 87 ± 9 y for Sm¹⁵¹, 134.2 ± 0.8 d for Tm¹⁷⁰, 700± 5 d for Tm¹⁷¹, 3.68 ± 0.05 y for Tl²⁰⁴, and 164.4 ± 0.4 d for Cm²⁴². These data are compared with current literature values, and average values of the existing determinations are given.