Theoretical calculations of high-resolution X-ray spectra
An important goal in X-ray spectroscopy of transition metals is to obtain spectra with sufficiently high resolution (<0.1 eV) so that the main electronic transitions can be observed. This has been a major challenge for enzymes and catalytic systems that are probed using hard X-rays. However, with recent progress in instrumentation, and the use of resonant inelastic X-ray scattering (RIXS), this challenge can be overcome. These experimental developments call for matching progress in modeling. Studies of transition metals require a method that correctly describes both multiplet effects and the effects of spin-orbit coupling. The aim of the current project is therefore to develop a theoretical approach, based on multiconfigurational wavefunction theory, to model high-resolution X-ray spectra of transition metal catalysts. This approach will then be used to interpret RIXS spectra of water oxidation catalysts in solar fuel systems, which will lead to a better understanding of their catalytic efficiency. However, the modeling approach can be used for a wide range of X-ray processes, including time-resolved studies, and has the potential to become a key tool for the interpretation of experiments from new high-brilliance X-ray sources.