EXAFS analysis of the L-3 edge of Ce in CeO2: effects of multielectron excitations and final-state mixed valence

Cerium oxide (IV) (CeO2) is extensively employed in heterogeneous catalysis , particularly as a promoter of noble metal action in three-way catalysts. For this reason there is a great scientific and economical interest in the development of any possible chemical or structural analysis technique that could provide information on these systems. EXAFS spectroscopy has revealed itself as a powerful technique for structural characterization of such cat alysts. Unfortunately good quality K-edge spectra of cerium are not yet eas ily obtainable because of the high photon energy required (>40 keV). On the other hand, at lower energies it is easy to collect very good spectra of t he L-3 edge (5.5 keV), but L-3-edge spectra of cerium (IV) are characterize d by the presence of two undesired additional phenomena that interfere with EXAFS analysis: final-state mixed-valence behaviour and intense multi-elec tron excitations. Here, a comparative analysis of the K, L-3, L-2 and L-1 e dges of Ce in CeO2 has been made and a procedure for obtaining structural p arameters from L-3-edge EXAFS, even in the presence of these features, has been developed. This procedure could allow further studies of catalytic com pounds containing tetravalent cerium surrounded by oxygen ligands.