Search for ground state proton emission fromAs65andBr69

Abstract

The ground state proton decays of ${}_{}{}^{65}{}_{}{}^{}\mathrm{As}$ and ${}_{}{}^{69}{}_{}{}^{}\mathrm{Br}$ have been searched for in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ and ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ bombardments of a natural calcium target. These studies employed a newly developed rapidly rotating recoil-catcher wheel and a low-energy particle-identification telescope. No proton groups that could be assigned to either of these nuclides were observed. The minimum detectable limits indicate that ${}_{}{}^{65}{}_{}{}^{}\mathrm{As}$ and ${}_{}{}^{69}{}_{}{}^{}\mathrm{Br}$ either decay predominantly by beta emission or have half-lives less than 100 μs. The overall evidence strongly indicates that ${}_{}{}^{65}{}_{}{}^{}\mathrm{As}$ predominantly beta decays.