Absorption of hard γ-rays by elements

Abstract

In this paper an account will be given of an accurate determination by a balance method of the relative absorption in a large number of elements of γ -radiation from Ra B + C filtered through 1 cm. of lead. The object of these experiments was to find out whether there is a simple relation between the absorption in an element and its atomic number, and also whether the nuclear electrons make a sensible contribution. As a result of these measurements, it will be shown that the laws of absorption of γ -rays of high frequency can be linked up with the corresponding laws known for X-rays of much lower frequency. A mutual comparison will also throw some light on the relative part played by scattering and true absorption in the passage of penetrating radiation through matter. An account of earlier work on the absorption of γ -rays by matter will be found in the standard works on radioactivity— e. g. , by Rutherford (1913) and by Meyer and Schweidler (1916). It is, however, necessary to mention briefly some results of the later work relevant to the present experiments.