Positron mean free paths between 50 eV and 40 keV

We have developed a formalism for calculating the inelastic mean free paths (IMFP's) of positrons by extending an existing semiempirical method developed by Tanuma, Powell, and Penn that is currently used for electrons. As examples, we have calculated the positron IMFP's in the 50 eV to 40 keV energy range for four different elements. In the intermediate-energy region, roughly 200 eV to 2 keV, the inelastic mean free paths for both positrons and electrons are similar. However, at lower energies, differences in correlation and exchange between the leptons during inelastic scattering events result in the inelastic mean free path being smaller for the positrons than for the electrons. At the highest energies, above about 2 keV, the relativistic correction suggested by Inokuti to the scattering cross section has been made. The resulting relativistic inelastic mean free paths are reasonable upper limits for both leptons below the bremsstrahlung regime.