DELOCALIZATION IN ELECTRON-IMPACT IONIZATION IN A CRYSTALLINE ENVIRONMENT

A theory for variations in cross section with diffraction conditions for electron-impact ionization of atoms in a crystalline environment is presented. This takes into account total interaction delocalization (due both to long-range Coulombic interaction and thermal smearing of the target position) by integration over all scattering angles and ejected electron momenta as well as attenuation of dynamical effects by inelastic scattering, particularly thermal diffuse scattering. These results are of fundamental importance for atom location by channeling-enhanced microanalysis using energy-dispersive x-ray or electron-energy-loss-spectroscopy techniques. Agreement between this theory and various energy-dispersive x-ray experiments reported in the literature (as well as our own experiments) under dynamical electron-diffraction conditions is satisfactory.