Theory of multi-atom resonant Raman scattering

Abstract

We theoretically study X-ray resonant Raman scattering where the incident photon energy ωλ is tuned near deep core threshold, and the scattered one ωλ′ is tuned so that ωλ−ωλ′ should be near shallow core threshold: In contrast to ordinary resonant inelastic X-ray scattering (RIXS), they are on different atomic sites. The many-body scattering theory developed by Almbladh and Hedin has been extended to include multi-atom resonant effects. A quite similar formula to multi-atom resonant photoemission (MARPE) was obtained, which cannot be observed in the highly symmetric environment around the shallow core hole sites. In comparison with RIXS, a further non-radiative processes has to be taken into account between the two radiative interactions in the scattering amplitude. The structure factors severely control the possibility to observe MARX-Raman scatterings. They are in the order of R−2 which is in contrast to the order of R−3 for the structure factors in MARPE: R is the distance to the nearby atoms. The condition where we cannot observe MARX-Raman spectra is different from that for MARPE spectra. For the systems with spatial inversion symmetry around the shallow core hole site, we cannot expect to observe the MARX-Raman spectra. For some oxides including heavy metals like PbO and Ag2O, though they are in low symmetries around oxygens, we cannot expect to observe the MARX-Raman spectra due to the structure factors.