New Isomers of Astatine-212

Abstract

The ${}_{83}{}^{}{}_{}{}^{}\mathrm{Bi}_{}^{209}{}_{}{}^{}(\alpha , n){}_{85}{}^{}{}_{}{}^{}\mathrm{At}_{}^{212}{}_{}{}^{}$ reaction was investigated in the energy range of 17 to 25 MeV. Astatine-122 was observed to decay by alpha-particle emission. An alpha decay group of 7.60 and 7.66 MeV having a half-life of 0.305 sec and another group of 7.82 and 7.88 MeV having a half-life of 0.120 sec were observed. Relative excitation functions were obtained for both isomers. An energy-level diagram for the alpha decay of astatine-212 is proposed.