Real Space Green's Function Approach to Resonant Inelastic X-Ray Scattering and HERFD XAS

We present a theory of resonant inelastic x-ray scattering (RIXS) and high energy resolution fluorescence detected (HERFD) x-ray absorption spectra (XAS) based on the real space multiple scattering Green's function formalism. The Kramers-Heisenberg formula is transformed into an expression involving Single particle Green's functions. Simplifying assumptions give the RIXS cross section in terms of a convolution of an effective absorption spectrum with the x-ray emission spectrum. Given the RIXS cross section, calculations of the HERFD XAS are also possible. Self-energy effects are calculated using an efficient many-pole model. Further many-body effects can be treated via a convolution with an effective spectral function. The approach is implemented as an extension of the FEFF9 code. Calculated results are compared with experimental RIXS of WO2.