The half-life of AcC' (Po211) has been measured for the first time, and is 0.52 second rather than the 1200 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 Bi211 (T12=2.16 min) and two states of Po211 (T12=25 and 0.52 ) 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 Po211, with an excitation energy of about 0.3 Mev. A group of alpha particles having about 9-Mev energy was observed but not identified.