Effect of Inelastic Scattering on Mean and Anomalous Absorption Coefficients of Electrons in Magnesium Oxide Crystals Studied by Electron Microscope

The intensity of equal-thickness fringes of magnesium oxide is measured by a photometric method. Taking advantage of the chromatic aberration of the electron microscope, the intensity due to elastically scattered electrons and that to inelastically scattered electrons are measured separately. The latter is comparable to the former at the crystal thickness of 200Å and about ten times the former at 1,000Å. This means that the anomalous transmission effect is mainly caused by inelastically scattered electrons. Equal-thickness fringes are produced not only by elastically scattered electrons but also be inelastically scattered electrons with energy loss. The mean and anomalous absorption coefficients are measured for elastically scattered electrons and the results are compared with theoretical values.