The phosphorescence produced by the α- and β-rays

Abstract

The radiations from radio-active substances share with light and other radiations the property of exciting luminosity in various substances. These substances require in general to have a small amount of impurity present, and in many cases they appear to lose their sensitiveness under the prolonged action of the radiation. Thus Beilby has shown that barium platinocyanide after continued exposure to the β-rays assumes a reddish-brown colour, while the luminosity excited by the rays falls off considerably. Also it is well known that the zinc sulphide screens of spinthariscopes after a time need renewal owing to their luminosity becoming fainter. As the experiments of Rutherford and Geiger have shown that the scintillation property of zinc sulphide can be used for quantitative measurements of substances emitting α-particles, it has become of interest to investigate the nature of this effect. The following questions have, therefore, been examined.