Simultaneous diffraction. Indexing unweganregung peaks in simple cases

By simultaneous diffraction is meant those diffraction effects which occur when a single crystal is so oriented that more than one Bragg reflection is operative for a given monochromatic ray. These effects often are apparent on films and may seriously modify intensity measurements in Geiger counter diffractometry. The indexing of the planes involved in one class of these effects; namely, umweganregung, is worked out in some detail. Umweganregung peaks may be used as a precise measure of lattice parameter, as pointed out by Renninger.