Alpha-Decay Energies of Polonium Isotopes

The isotopes ${\mathrm{Po}}^{200}$ and ${\mathrm{Po}}^{201}$ have been shown to have half-lives of 11 and 18 minutes, respectively, and to emit alpha-particles of 5.84 and 5.70 Mev. Both isotopes decay mainly by electron capture. The energies of the alpha-particles of the polonium isotopes 206 to 209 have been redetermined as 5.21, 5.10, 5.10, and 4.86 Mev, respectively. The abundance of the low energy alpha-group of ${\mathrm{Ra}}^{226}$, which was used as a standard in this work, was observed as 4.8 percent of the total alpha-activity.