Experimental determination of x-ray resonant Raman scattering cross-sections for several elements and compounds

HECTOR JORGE SANCHEZ; M.C. VALENTINUZZI; J. ABRAHAM; C. A. PÉREZ

París (Francia)

Congreso; EXRS 2006; 2006

The x-ray resonant Raman scattering (RRS) is an inelastic process that occurs when an atom interacts with an incident photon having an energy slightly lower than that of one of the absorption edge. For an interaction in the 1s states, the two-state model considers a virtual K-hole in the intermediate state and a final state with an L-hole (or M-hole) , an electron in the Fermi levels (or in the continuum) and a x-ray photon.  X-ray resonant Raman scattering was observed for the first time many years ago, nevertheless there is a lack of knowledge  about cross sections and their energy dependence. Some authors have reported  deviations between the measured values of mass attenuation coefficient and the corresponding theoretical ones of the order of 10%. For this reason a precise determination of RRS cross sections will contribute to improve the current values of photoelectric absorption coefficient. In addition, resonant Raman scattering can produce, under certain experimental conditions, unexpected peaks in x-ray fluorescence spectra. This work presents experimental measurements of x-ray resonant Raman scattering for Fe, Cu, Zn and different copper oxides. In addition, measurements of RRS for the L-edge of Er are also presented. The measurements were carried out in the XRF station of the LNLS using monochromatic synchrotron radiation. Several energy scannings were performed to analyze the Raman peak (below the threshold), the energy of the absorption edge, and the fluorescent line (above the absorption edge) in order to determine the resonant Raman yield. Data analysis includes several complex stages including non-linear fittings, theoretical cross-sections convolutions, instrument-function deconvolutions, etc. The results agree very well with previous measurements published by other authors for the case of Fe, Zn and pure Cu. The results for the L-edge RRS cross sections are the first one ever reported. Finally, the analysis of different oxides of Cu showed variations depending on the oxidation state.