The Emission ofLX-Rays of Lead inPo210Decay

By use of a proportional counter x-ray spectrometer, it is established that ${\mathrm{Po}}^{210}$ sources emit characteristic $L$ photons of Pb, in yield 2.93×${10}^{-4\mathrm{}}$(±15 percent) per alpha-particle. The excitation of these photons is ascribed to the ejection of $L$ electrons from the electronic cortege of the nucleus in the act of alpha-decay, in a manner treated by Migdal's theory. The probability of $L$ electron ejection is about 8.8×${10}^{-4\mathrm{}}$ per alpha-particle, as computed from the observed photon yield and Kinsey's fluorescence yields. The theory in its present state accounts for only 13 percent of the photons observed.