The Secondary Structure of X-Ray Absorption Edges from Elements in Certain Cubic Crystals

The $K$ x-ray absorption spectra of potassium, chlorine, calcium and sulfur in several different cubic crystals have been photographed. The absorption spectrum was obtained for potassium from filters prepared with KF, KCl, KBr and KI, and the chlorine spectrum from LiCl, NaCl, KCl, RbCl. The calcium and sulfur absorption spectra were obtained from powdered calcium sulfide. A secondary structure was found on the short wave-length side of the $K$ edge of each of these elements. The following results are not in accord with the demands of the Kronig theory for secondary structure:—The absorption spectra of two elements in the same crystal are not similar. The product of the separation of each of the secondary structure components in volts and the square of the lattice space is not a constant for the crystals studied. Some of the structure previously reported for the sulfur edge is shown to be due to the sulfur contained in goldbeater's skin which had been used to cover the slit of the x-ray tube.