LIII-XAS theory in light rare earth metallic compounds

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Abstract
The authors present a first calculation of the 2p to 5d X-ray absorption (LIII-XAS) in light rare earth metallic compounds by using the Anderson impurity model in relation with recent LIII-XAS experiments. The results are exact in the limit of large degeneracies Nf and Coulomb interaction Uff to infinity . Hybridisation V between localised 4f and extended 5d states is shown to be determinant in both the initial and the final states of the photo-absorption process and a close relationship through a convolution is established between the core XPS and the LIII-XAS spectra from symmetry requirements. The authors discuss the absorption spectra with respect to the valence of the considered compound as well as to the parameters entering the model (f position, V, Ufc, density of states etc.). They obtain a good agreement with the experimental data (XPS, XAS) especially for LaPd3 compounds and for the gamma alpha transition in cerium, and show that the LIII-XAS spectra allow one in general to obtain a reliable value for the ground state valence.