Ionization by impact electrons in solids: Electron mean free path fitted over a wide energy range

We propose a simple formula for fitting the electron ionization mean free paths in solids both at high and at low electron energies. The free-electron-gas approximation used for predicting electron mean free paths is no longer valid at low impact energies [(E−EF)<50eV], as the band structure effects become significant at those energies. Therefore, we include the results of band structure calculations in our fit. Finally, we apply the fit to nine elements and two compounds.