Energy shift and structure of the K-absorption edge of vanadium in some vanadium compounds

The energy shift of the K-absorption edge of vanadium and the associated fine structure have been investigated for the following chemical compounds: V, VO, V2O3, V2O4, V2O5, VC, VN, VB2, VSi2, VF3, and VS3. All measurements were made with an improved version of a single-crystal high-angle goniometer. All studied samples except V2O5 exhibit an extended structure on the high-energy side of the absorption edge. Shoulders, on the absorption edge proper, were observed with several samples, and well-resolved "white" lines were found on the low-energy side of the edge of vanadium in the following compounds: VO, V2O5, and V2S3. The chemical energy shift of the K-absorption edge, which is found to be governed by the effective ionic charge on the absorbing atom and the structure in the vicinity of the edge are discussed on basis of the molecular-orbital theory.