Combining theoretical chemistry and XANES multi-edge experiments to probe actinide valence states

Both structural and electronic properties of the actinide cations are of fundamental interest in order to describe the intramolecular interactions. The 5f and 6d orbitals are the first partially or totally vacant states of these elements and their properties reflect the nature of the actinide-ligand bond. Because of its chemical and orbital selectivities, XANES spectroscopy is useful to probe the actinides' frontier orbitals and then understand the cation reactivity toward chelating ligands. The actinicle L-3 edge contains structural information on the coordination polyhedron. because of important scattering features. But very little electronic information can be extracted, due to the short core-hole lifetime, broadening the edge signal. On the other hand, the actinide M-4.5 edges provide a better resolution and allow one to achieve electronic and structural information. Furthermore, coupling simulations of the experimental spectra and quantum chemical calculations lead to quantitative information such as the determination of the actinide coordination sphere and its effective charge.