Core-to-core resonant inelastic x-ray scattering (RIXS) and valence-to-core RIXS techniques are two complimentary ways for probing the electronic structure in actinide systems. Specific cuts of the core-to-core RIXS maps around Mβ and Lαlines of actinides represent remarkably improved high-resolution x-ray absorption spectra of actinide 3d and 2p edges, respectively, as a result of limited lifetime broadening of core holes present in shallower levels in the final state of the spectroscopic process. That allows for more detailed studies of unoccupied states and better oxidation states assignments. In turn, the valence-to-core RIXS spectra are only limited by the instrumental resolution and provide information about actinide chemical bonding and interactions between valence electrons.

 

A comparison of experimental data with results of model calculations shows that the resonant spectra of actinide systems recoded at the actinide M(3d) and O (5d) thresholds which probe the 5f states can be interpreted using the many-body theory, such as the Anderson impurity model, while the data obtained at the L3 threshold and representing the 6d states of actinides can be described within a single-particle approach, such as LDA+U (local density approximation with supplemented Coulomb interaction U) framework.

 

In course of discussion of the above statements, we present the RIXS data for a number of actinide systems with emphasis on the results contributing to understanding of the U-O and Pu-O phase diagrams, in particular data for UO2+x, U4O9, U3O8 and PuO2+x. The influence of the Coulomb interaction between 5f electrons on the electronic structure of actinides is also discussed.