Alpha Decay ofU227

The $\alpha$ spectrum of the ${}_{}{}^{227}{}_{}{}^{}\mathrm{U}$ decay chain, previously reported in 1952 by Meinke et al., was investigated by bombarding ${}_{}{}^{231}{}_{}{}^{}\mathrm{Pa}$ with protons from 35 to 54 MeV. The half-life of the parent nuclide ${}_{}{}^{227}{}_{}{}^{}\mathrm{U}$ was found to be 1.1±0.1 min, in agreement with the earlier value of 1.3±0.3 min. The $\alpha$-particle energies in the decay chain were determined more precisely than in the earlier study. In addition, some disagreement was found with the 1952 work. The nuclides and $\alpha$-particle energies observed in the present investigation are as follows: ${}_{}{}^{227}{}_{}{}^{}\mathrm{U}$, 6.87±0.02 MeV; ${}_{}{}^{223}{}_{}{}^{}\mathrm{Th}$, 7.33±0.02 MeV; ${}_{}{}^{219}{}_{}{}^{}\mathrm{Ra}$, 7.70±0.02 MeV (relative intensity 0.7±0.1) and 7.99±0.02 MeV (0.3±0.1); ${}_{}{}^{215}{}_{}{}^{}\mathrm{Rn}$, 8.67±0.02 MeV; and ${}_{}{}^{211}{}_{}{}^{}\mathrm{Po}$, 7.46±0.02 MeV.