Influence of the geometric structure on the V L₃ near edge X-ray absorption fine structure from vanadium phosphorus oxide catalysts

We present the V L3 near edge X-ray absorption fine structure (NEXAFS) of a vanadium phosphorus oxide (VPO) catalyst. The spectrum is related to the V3d-O2p hybridised unoccupied states. The overall peak position at the V L3-absorption edge is determined by the formal oxidation state of the absorbing vanadium atom. Details of the absorption fine structure are influenced by the geometric structure of the compound. Empirically we found a linear relationship between the energy position of several absorption resonances and the V-O bond length of the participating atoms. This allows to identify the contribution of specific V-O bonds to the near edge X-ray absorption fine structure. The bond length / resonance position relationship will be discussed under consideration of relations between geometric structure and NEXAFS features observed in X-ray absorption experiments and theory