LOW-ENERGY-ELECTRON ATOM ELASTIC-SCATTERING CROSS-SECTIONS FROM 0.1-30 KEV

Empirical forms for electron/atom scattering cross sections predict backscattering factors that compare well with those calculated using tabulated Mott data from 0.1 to 30 keV. The form of the empirical total cross section is similar to the screened Rutherford cross section. The fit to the tabulated differential Mott cross sections is decomposed into two parts, one part being of the same mathematical form as the screened Rutherford cross section (sigma(R)), and the second part being an isotropic distribution (sigma(I)). The ratio of the total cross sections (sigma(R)/sigma(I)) between the screened Rutherford part of the differential scattering cross section and the isotropic part of the distribution is fitted to give the same ratio of forward to backscattered cut-rents as the tabulated Mott differential cross sections. The three equations, one for the total elastic cross section and two describing the differential cross section-one for the Rutherford screening parameter and one for the ratio sigma(R)/sigma(I)-give backscattering results covering ah the major trends with energy and atomic number compared with the backscattering coefficients calculated using tabulated Mott cross sections. However, agreement with experiment is poor for some well-researched examples such as Au. Monte Carlo calculations using the empirical cross sections show that surface effects may be critical in interpreting experimental results.