Two-Crystal Study of the Structure and Width ofKX-Ray Absorption Limits

The double-crystal spectrometer has been used to examine the $K$ absorption limits of the elements Se, Rb, Zr, Mo and compounds of these elements. All of the substances examined show structure either on the short wave-length side of the main absorption limit or in the limit itself. The intensity and location are discussed with reference to the theory of secondary structure given by Kronig. The widths of the absorption limits have been measured and it is shown that the widths are approximately constant for elements of atomic number less than 32 and that from there on they increase as the fourth power of the atomic number.