X-ray absorption near-edge spectra and electronic structure of rhodium compounds

Theoretical and experimental Rh L edge X-ray absorption near-edge spectra (XANES) in the compounds RhCl₃, Rh₂O₃ and (Rh(CO)₂Cl)₂ are presented. L₁ and L _2,3 pre-edge features (bound to bound state transitions) and near-edge features (continuum final states) are analysed and used to interpret experimental L₃ spectra. The self consistent-field local density theory was used to calculate charge densities and potentials, as well as densities of states in an embedded cluster approach. Multiple-scattering theory was used to determine the final states, and the absorption cross-section was calculated in the dipole approximation. Quantitative modelling of the absorption spectra permits derailed assignment of individual absorption features due to effective atomic configurations and local geometrical effects. The off-site Rh 4f resonance is a notable feature of the XANES which may be useful in characterizing Rh-Rh interaction.