Predictive X-ray spectroscopy of actinide complexes: from HERFD-XANES to RIXS maps via relativistic quantum chemistry
Résumé
High-energy-resolution X-ray spectroscopies such as HERFD-XANES and Resonant Inelastic X-ray Scattering (RIXS) are powerful probes of actinide electronic structure and coordination. Predictive theoretical descriptions are particularly challenging for poorly characterized actinides.
We combine HERFD-XANES experiments with relativistic quantum chemical calculations to study uranium(VI) and protactinium(V) complexes of environmental relevance. Uranyl
compounds with varying ligand fields and O=U=O bending serve as benchmarks; U M4-edge HERFD-XANES spectra are interpreted using relativistic time-dependent density functional
theory (TD-DFT) [1,2].
The focus is then placed on protactinium(V) [3]. HERFD-XANES spectra at the Pa L3-edge in hydrofluoric and oxalic acid solutions show closely related features, raising questions about Pa(V)
speciation and oxo bonding. These spectra are analyzed using TD-DFT together with multi-reference spin–orbit SO-RASSCF and SO-RASPT2 calculations.
Predictive Pa L3-edge RIXS maps, computed exclusively with SO-RASSCF/SO-RASPT2, reveal sensitive fingerprints of metal-centered and charge-transfer excitations, providing clear targets for
future high-resolution RIXS experiments on protactinium complexes.
References:
[1] W. A. Misael, A. S. P. Gomes. Core excitations of uranyl in Cs2UO2Cl4 from relativistic embedded damped response time-dependent density functional theory calculations. Inorg. Chem. 2023, 62, 29, 11589–11601.
[2] W. A. Misael, J. März,, L. Amidani, E. F. Bazarkina, K. O. Kvashnina, V. Vallet, A. S. P. Gomes. Core-Excited States of Linear and Bent Uranyl Complexes: Insights from High-Energy Resolution X-ray
Spectroscopy and Relativistic Quantum Chemistry. Inorg. Chem. 2025, 64, 45, 22487–22502.
[3] M. Maloubier, T. Shaaban, F. Réal, C. Le Naour, H. Oher, T. Aubert, P. L. Solari, B. Siberchicot, R. Maurice, V. Vallet. Speciation of Protactinium(V) in Hydrochloric Acid solutions: evidence of the
Protactinium(V) Monooxo Bond Stability, Angew. Chem. Int. Ed. 2025, e18403.