Spectrum of Cosmic Radiation

Abstract

COSMIC radiation forms a whole series of lines or bands in its spectrum, as can be established by measuring its absorption coefficient. The most penetrating of its constituents, having energy of about 3700 million volts, originates, according to Sir James Jeans, in the annihilation of an α-particle and its two neutralising electrons,¹ while the next softer constituent, of energy about 950 million volts, is formed by the annihilation of one proton and its neutralising electron. In both these cases, as generally accepted, one can scarcely suggest any other interpretation. The interpretation, however, of the softer constituents by the formation of helium and higher atoms from ‘metastable clusters’ consisting of protons and electrons, as suggested by Prof. R. A. Millikan,² has supplemented the first assumption of the origin of cosmic radiation : Proton + Electron = hv, made by Sir James Jeans, which seemed unable to give more than one line and did not indicate any logical or numerical connexion between the energy value of the proton-annihilation constituent and those of softer ones.