K-SHELL IONIZATION UNDER ZONE-AXIS ELECTRON-DIFFRACTION CONDITIONS

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 chro mia under zone-axis diffraction conditions for 300-keV electrons. X-ra y counts as well as backscattered-electron contrast are recorded as th e beam is tilted by about 70 mrad on a two-dimensional scan raster. Ca lculated K-shell ionization and backscattering cross sections, based o n a model which takes into account interaction delocalization, thermal diffuse scattering, and the consequent thickness-dependent channeling effects in a realistic way, are in good agreement with experiment.