Understanding the electronic structure and bonding properties of the actinide elements by applying high resolution X-ray spectroscopy and computations

Understanding the electronic structure and chemical bonding properties of the actinide (An) elements poses a great challenge and frontier in fundamental chemistry and physics.1 The An M4,5 absorption edge core-to-core and valence band resonant inelastic X-ray scattering (CC/VB-RIXS) and high energy resolution X-ray absorption near edge structure (HR-XANES) techniques probe the occupied and unoccupied parts of the valence band of the actinide elements with extraordinary energy resolution and thus unique information on the chemical bond can be obtained.1 A deep insight into the An electronic structures is for example essential to understand actinide environmental behaviour. The An M4,5 edge RIXS and HR-XANES studies are performed at the ACT station of the CAT-ACT beamline at the KIT Light Source, KIT, Germany. 2
Spectroscopic and computational tools for probing in detail the An-ligand (U, Np, Pu or Am) bond covalency will be discussed.1, 3-5 It will be shown that An 3d4f CC-RIXS can be used to measure spin-orbit coupling effects and is a probe of the localised and delocalised f electron density on the An atom. It will be demonstrated that the energy positions of the resonant peaks in the CC-RIXS/HR-XANES spectra strongly depend on the electron-electron/hole interactions in the intermediate and final state of the excitation process and thus these two effects are of importance for close agreement of calculated and experimental spectra.
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References: 1.Vitova, T.; Pidchenko, I.; Fellhauer, D.; Bagus, P. S.; Joly, Y.; Pruessmann, T.; Bahl, S.; González-Robles, E.; Rothe, J.; Altmaier, M.; Denecke, M. A.; Geckeis, H., The role Author name / Procedia Chemistry 00 (2023) 000–000 2 L of the 5f valence orbitals of early actinides in chemical bonding. Nature Communications 2017, 8, 16053. 2.Schacherl, B.; Prussmann, T.; Dardenne, K.; Hardock, K.; Krepper, V.; Rothe, J.; Vitova, T.; Geckeis, H., Implementation of cryogenic tender X-ray HR-XANES spectroscopy at the ACT station of the CAT-ACT beamline at the KIT Light Source. Journal of Synchrotron Radiation 2022, 29 (1), 80-88. 3.Bagus, P. S.; Schacherl, B.; Vitova, T., Computational and Spectroscopic Tools for the Detection of Bond Covalency in Pu(IV) Materials. Inorganic Chemistry 2021, 60 (21), 16090-16102. 4.Vitova, T.; Pidchenko, I.; Schild, D.; Prüßmann, T.; Montoya, V.; Fellhauer, D.; Gaona, X.; Bohnert, E.; Rothe, J.; Baker, R. J.; Geckeis, H., Competitive Reaction of Neptunium(V) and Uranium(VI) in Potassium–Sodium Carbonate-Rich Aqueous Media: Speciation Study with a Focus on High-Resolution X-ray Spectroscopy. Inorganic Chemistry 2020, 59 (1), 8-22. 5. Polly, R.; Shacherl, B.; Rothe, J.; Vitova, T., Relativistic Multiconfigurational Ab Initio Calculation of Uranyl 3d4f Resonant Inelastic X ray Scattering, Inorganic Chemistry 2021, 60, 18764−18776