Sm157, a New Isotope

Irradiation of enriched ${}_{}{}^{160}{}_{}{}^{}\mathrm{Gd}$ with fast neutrons was found to produce a new radioactivity which was assigned to the ($n,\alpha$) product ${}_{}{}^{157}{}_{}{}^{}\mathrm{Sm}$. The following radiation characteristics were observed to belong to ${}_{}{}^{157}{}_{}{}^{}\mathrm{Sm}$: half-life 83 ± 2 sec, $\gamma$-ray energy 121.5 ± 0.5 keV, and maximum ${\beta }^{-}$-ray energy 2.83 ± 0.05 MeV.