The interplay of the 3d⁹ and 3d¹⁰ electronic configurations in the copper K-edge XANES spectra of Cu(II) compounds

A theoretical analysis of the X-ray absorption near-edge structure spectra at the Cu K-edge in several divalent copper [Cu(II)] compounds showing a distorted nearest-neighborhood around copper is presented. The experimental spectra of CuO and KCuF₃ have been compared with computations performed in the framework of the multiple-scattering theory. The results show that ab initio single-channel multiple-scattering calculations are not able to reproduce the experimental spectra. On the contrary, the experimental spectra can be accounted for by using two excitation channels and the sudden limit of the multichannel multiple-scattering theory. The comparison between experimental data and computations indicates that both 3d⁹ and 3d¹⁰ electronic configurations are needed to account for the absorption process in these systems, suggesting that this is the general case for the K-edge XANES of divalent copper compounds.