Absorption of Cosmic Rays

Abstract

THE Klein-Nishina formula, which is based on the scattering and absorption of X- and -radiation by extra-nuclear electrons, has been widely used in the calculation of the absorption coefficients of high-frequency quanta. But recent experimental work and theoretical deductions have shown that this formula is not applicable to the absorption of -radiation of energy greater than 1.0 × 106 e.v., since for higher energies there is additional absorption due, in the main, to interactions between the radiation and atomic nuclei, these interactions giving rise to electron pairs. This nuclear absorption, which becomes of greater importance as the energy of the quanta increases, and is probably the predominant type of absorption which would occur with any ultra -radiation arising from actions such as the condensation or annihilation of protons and electrons in space, is not accounted for by the Klein-Nishina formula. The latter cannot, therefore, be directly applied to the cosmic ray problem as has been previously assumed, and the wave-lengths of supposed photon components calculated by means of this formula must be inaccurate, since the formula does not take into account the nuclear absorption.