The upper limit of energy in the spectrum of radium E

Abstract

The disintegration of radium E has for some years attracted considerable attention. It is distinguished from the majority of β-ray bodies by the fact that there are no traces of peaks, due to homogeneous radiation, superimposed on the continuous spectrum of the disintegration electrons. It seems clearly established from the work of Ellis and Wooster, and of Meitner, on the heating effect of radium E, that the β-rays from this body are initially inhomogeneous when emitted from the nuclei. It is obviously of considerable interest to determine the velocity with which the fastest of the particles emerge from the nucleus; in other words the “ end point ” of the β-ray spectrum. The existence of such an upper limit in the case of radium E was first sug­gested by Gray, who observed an end point or kink in the β-ray absorption curve. Madgwick investigated the continuous distribution of the particles by means of an ionisation chamber and magnetic deflection, and found a fairly definite end point, such as Gurney║ had observed in the case of radium (B + C). Madgwick gave this end point as 5000 Hρ, corresponding to an upper limit of energy of 1,070,000 volts.