Diffraction contrast retained by plasmon and K-loss electrons

A theory developed by Rez and co-workers for phonon scattering of fast electrons in crystals has been used to predict the plasmon loss and K-shell loss distribution in diffraction patterns. This shows clearly how energy loss analysis may yield spurious results when used for the quantitative detection of light elements. Calculations show varying diffraction contrast in the plasmon loss beam when an objective aperture is displaced in different directions from diffracted beams, and are in good agreement with experiment. It is shown that, in weak-beam techniques, inelastic scattering by electronic excitations from neighbouring beams in a systematic row should raise background but not interfere with diffraction contrast. (orig.)