X-ray intensity measurements on large crystals by energy-dispersive diffractometry. II. Energy dependence of the Friedel pair intensities and their ratio near the absorption edge

It has experimentally and theoretically been confirmed that the intensity ratio r_h of Friedel pair reflexions h and is given by |F_h|²/|F² in a perfect crystal as well as in a mosaic crystal both in the symmetrical Bragg case and in the symmetrical Laue case. The measurements have been carried out on a nearly perfect GaAs crystal plate in the energy range near the As K absorption edge by the use of the energy-dispersive diffractometer and continuous radiation. These results have shown, a reasonable agreement with the relevant theoretical curves. The limitation of the above relation in tile presence of extinction effects has been considered.