The Disintegration of Radium D

The disintegration of radium D has been investigated using a gaseous source of lead tetramethyl in a proportional counter. The form of the low energy $\beta$-spectrum coincident with the 46.7-kev $\gamma$-ray has been determined. The end point has been found to be 15.2±1 kev. The shape of the spectrum shows good agreement with the Fermi theory for an allowed transition, in which the effect of screening on the Coulomb factor is neglected. The results indicate that the number of $\beta$-particles below 3 kev is somewhat less than than predicted by theory, neglecting screening. It is also concluded that the change in binding energy of the atomic electrons (about 10 kev) released in the decay, is included in the energy of disintegration of the $\beta$-particles, and is shared between the $\beta$-particle and neutrino.