Electron inelastic mean free paths for plasmon excitations and interband transitions

Both plasmon excitations and interband transitions are important in the response of valence bands to fast electrons. An extended Drude dielectric function was established to describe such a response in solids of complex band structures. Parameters in this function were determined by a fit of the imaginary part of the function to experimental optical data. The real part of the dielectric function and the energy-loss function were also checked with experimental data to confirm critical-point energies in the interband transitions and plasmon energies in the collective excitations. In addition, sum-rules about the imaginary part of the dielectric function and the energy-loss function, respectively, were applied to assure the accuracy of these functions. Electron inelastic mean free paths in several solids were calculated and compared to available experimental and theoretical data.