LI. Low-velocity X-ray electrons

Abstract

It is shown that the normal component of the velocity of over 85 per cent. of the electrons emitted from a gold film under the influence of a heterogeneous beam of X-rays is less than 2 volts. The distribution with velocity bears a relationship to that of the thermions from a hot body. It is argued that the mode of production of these slow electrons can scarcely be due to atomic recoil consequent on the ejection of a rapid β-ray nor to the action of the transformed X-ray energy into energy of longer wave-length. The analogy with the thermionic process probably arises from the fact that in both cases only the outermost system of electrons take part in the action, though the mechanism of the two processes must differ considerably, in the present case the intermediary being the rapid primary β-ray. The distribution with velocity of the electron atmosphere, from the point of view of thermionics in the case investigated, corresponds to a temperature of 11,000° abs. It becomes important, therefore, to investigate under all conditions the correspondence between the two processes. A “null” method of using an electroscope is described.