The Effect of Screening on Beta-Ray Spectra and Internal Conversion

Abstract

The Dirac equation for an electron in the field of a Thomas-Fermi-Dirac atom is solved numerically on the ENIAC for a large number of cases. The resulting wave functions are used to calculate the effect of screening (by the atomic electrons) on allowed beta-spectra and on the internal conversion coefficients of gamma-rays. It is seen that the negatron spectra are essentially unaffected by screening; positron spectra are affected appreciably in a direction such as to increase the number of low energy positrons. Where a comparison can be made between the present calculations and previous ones in which the screening has been neglected, it is seen that the effect of screening is to increase the conversion coefficients slightly. Most of the present calculations, however, are for the soft gamma-ray region, for which only approximate formulas for the conversion coefficients exist. Thus the results of this paper are used to test the accuracy of these formulas. An attempt is also made to classify a number of experimentally observed gamma-rays.