X-Ray Emission Spectra of Sulphides and Sulphates

Abstract

A target for exciting x-ray emission spectra of chemical compounds is described. The wave-lengths of the $K\beta$ lines of alkaline earth sulphates and of some semiconducting sulphides are given. Using these results and the wave-lengths of the $K$ absorption edges, the energy gap between the occupied and unoccupied zones in these crystals is obtained. The results for the sulphates are compared with the results previously obtained for the corresponding sulphides. In order to account for the changes in emission wave-lengths from compound to compound, a nonuniform displacement of energy levels is needed in addition to the Madelung energy. A recent article by Slater and Shockley suggests one way in which this may be accomplished.