Gamma-Radiation from Polonium and from Lithium Bombarded with Alpha-Particles

IN connexion with the study of the secondary radiation emitted when a number of light elements were subjected in turn to the alpha-radiation emitted by a strong sample of polonium, Bothe and Becker1 found that polonium also emitted a hard gamma-radiation. The intensity of this was low, about one gamma-quantum being emitted for 105 alpha-particles. The gamma-radiation of polonium was interpreted as resulting from the fact that one of 105 alpha-particles was emitted with a lower energy than the rest, leaving the nucleus in an excited state, from which it returned to the ground-state with emission of a gamma-quantum. This gamma-quantum is able in its turn to release an electron from the new nucleus (RaG = Pb206) or the electron shell of nearby atoms, thus causing a secondary beta-radiation. Bothe2 investigated this beta-radiation with the aid of a beta-spectrograph of high light intensity (semi-circular method).