Abstract
On the basis of Lewis's theory of multiple scattering in an infinite medium, relatively simple expressions are obtained for the first and second moments of the electron distribution in depth, and for the second moment of the transverse distribution, as functions of atomic number and incident electron energy. The results are compared with some Monte Carlo calculations due to Bishop. These moments are then used to determine semi-empirical expressions for the distribution functions. These results are compared with the Monte Carlo distributions for copper, in which instance good agreement is found. Some discussion is given of the applicability of these results, and possible modifications, to the case of the semi-infinite medium.