Actinide and lanthanide speciation with high-energy resolution X-ray techniques

High-energy resolution X-ray absorption spectroscopy (HR-XAS) and Resonant inelastic X-ray scattering (RIXS) combined with quantum theoretical tools are gaining importance for understanding electronic and coordination structures of actinide (An) and lanthanide (Ln) materials. HR-XAS is successfully used to remove lifetime broadening by registering the partial fluorescence yield emitted by the sample, thereby yielding highly resolved X-ray absorption near edge structure spectra (HR-XANES), which often display resonant features not observed in conventional XANES. We demonstrate the structural characterization capabilities of these novel techniques by comparative discussion of U M4/L3-HR-XANES and L3-valence band RIXS (L3-VB-RIXS) spectra of two model U(VI) minerals. We show that the ab initio multiple scattering theory based code FEFF9.5 is an effective tool for calculations of An and Ln L3-HR-XANES and L3-RIXS spectra as it successfully reproduces dipole and quadrupole transitions in the same spectrum.