Proton Decay of an Intruder State inB185i

Abstract

The new proton radioactivity ${}^{185m}\mathrm{Bi}$ has been observed, produced via the ${}^{95}\mathrm{Mo}{(}^{92}\mathrm{Mo},pn{)}^{185}\mathrm{Bi}$ reaction. Its decay proceeds from the low-lying ${\frac{1}{2}}^{+}$ intruder state in ${}^{185}\mathrm{Bi}$ to the ${}^{184}\mathrm{Pb}$ ground state with the emission of a proton of energy $1.585\pm 0.009\mathrm{MeV}$ and a half-life of $44\pm 16\mu \mathrm{s}$. This marks the first observation of proton radioactivity above the $Z=82\mathrm{}$ closed shell, and it has been used to obtain the admixture of a $0^{+}$ intruder state in ${}^{184}\mathrm{Pb}$ into the ${}^{184}\mathrm{Pb}$ ground-state wave function.