CVII. The natural radioactivity of rubidium

Abstract

Abstract The radioactive decay of 87Rb has been studied using the scintillations; from a crystal of rubidium iodide activated with thallium, some fluorescent properties of which are described. This method free from source absorption and scattering troubles, indicates a β-spectrum with an end point of 275 kev. The Fermi plot gave a forbidden shape, for the most part close to that given by recent proportional counter work using 2π geometry, but having slightly more counts at the high energy end, and fewer at the low energy end ; the half-life has been determined at (5·90±0·3)×1010 years. The theoretical interpretations are indicated.