A Study of the K-edge Absorption Spectra of Selected Vanadium Compounds.

Abstract : High resolutions vanadium K-edge absorption spectra have been recorded for a number of selected vanadium compounds of known chemical structure using synchrotron radiation available at the Stanford Synchrotron Radiation Laboratory (SSRL). The compounds studied include oxides: VO, V2O3, V4O7, V2O4, and V2O5; vanadates: NH4VO3, CrVO4, and Pb5(VO4)3C1; vanadyl compounds: VOSO4-3H2O, vanadyl bis 1-phenyl 1,3-butane dionate, vanadyl phthalocyanine and vanadyl tetraphenylporphyrin; intermetallics: VH, VB2, VC, VN, VP, and VSi2; V2S3 and a vanadium-bearing mineral, roscoelite. Vanadium in these compounds exhibits a wide range of formal oxidation states (0 to +5) and coordination geometrics (octahedral, tetrahedral, square pyramid, etc.) with various ligands. The object of this systematic investigation is to gain further understanding of the details of various absorption features in the vicinity of the K absorption edge of a constituent element in terms of its valence, site symmetry, coordination geometry, ligand type, and bond distances. In particular the intensity and position of a well-defined pre-edge absorption in some of these compounds have been analyzed semi-quantitatively within a molecular orbital framework and a simple coordination charge concept. (Author).