A comprehensive theoretical treatment for the inelastic scattering of fast electrons in a crystalline environment is applied to account for variations in characteristic x-ray emission rates from spinel and chromia under zone-axis diffraction conditions for 300-keV electrons. X-ray counts as well as backscattered-electron contrast are recorded as the beam is tilted by about 70 mrad on a two-dimensional scan raster. Calculated K-shell ionization and backscattering cross sections, based on a model which takes into account interaction delocalization, thermal diffuse scattering, and the consequent thickness-dependent channelling effects in a realistic way, are in good agreement with experiment.

• Received 4 April 1994

DOI:https://doi.org/10.1103/PhysRevB.50.6673