Comparison of Experimental and Theoretical Values of Cross Sections for Electron Production by Proton Impact

Angle and energy distributions of electrons ejected from single- and multishell atoms by 50-to 300-keV protons are compared with various theoretical treatments. Partial cross sections for each subshell are calculated by scaling according to the number of electrons and the binding energy and then are added. The Born approximation fails at large and at small angles but yields fair agreement at intermediate angles. The treatments of Salin and of Macek, which take account of the influence of the projectile after the collision, yield much improved agreement at small angles. The binary-encounter model is used to calculate cross sections which are differential only in electron energy. An analytical expression is given for the binary-encounter cross section averaged over the Fock hydrogenic distribution of orbital velocities. When the average orbital energy is calculated from Slater's rules, the results agree somewhat better with experiment than when this energy is set equal to the binding energy.