Alpha-Emitting Isomer: Polonium-211

Abstract

The half-life of AcC′ (${\mathrm{Po}}^{211}$) has been measured for the first time, and is 0.52 second rather than the $\frac{1}{200}$ seconds widely quoted in the literature. Three short-lived alpha emitters resulting from alpha-particle bombardment of lead have been studied. They have been identified as ${\mathrm{Bi}}^{211}$ ($T_{\frac{1}{2}}=2.16\mathrm{}$ min) and two states of ${\mathrm{Po}}^{211}$ ($T_{\frac{1}{2}}=25\mathrm{} sec\mathrm{and}0.52sec$) by means of chemical separations, excitation functions, half-life measurements, and measurements of the energies of the emitted alpha particles. The energy measurements show that the 0.52-second state is an excited state of ${\mathrm{Po}}^{211}$, with an excitation energy of about 0.3 Mev. A group of alpha particles having about 9-Mev energy was observed but not identified.