Frank de Groot: Understanding Resonant Inelastic X-ray Scattering

The application and interpretation of X -ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS) will be discussed [1,2]. In 2p3d RIXS one scans through the 2p XAS edge and measures the optical excitation range. As an example, the RIXS spectra of CoO will be discussed. The experimental resolution of 100 meV allows the detailed observation of the electronic structure [3]. The resolution of x-ray emission detectors is expected to further improve giving rise to a more detailed view of the resonant excitations in the first 100 meV. The understanding of RIXS spectra needs the combination of (a) angular and polarization effects, (b) the eV scale (multiplet) electrostatic and crystal field interactions and (c) the meV scale magnetic, spin-orbit, vibration and symmetry distortion effects. Applying 2p3d RIXS to a mixed valence system under working conditions allows the detection of the optical spectrum of, for example, 1% Co2+ sites in a dominant Co3+ material. Related to the RIXS measurements is the analysis of Fluorescence yield (FY) detected x-ray absorption spectra (XAS), including the intrinsic deviations of FY-XAS spectral shape from the XAS spectrum [4,5].