Determination of the oxidation state by resonant-Raman scattering spectroscopy

Abstract

X-Ray fluorescence spectra present singular characteristics produced by the different scattering processes. When atoms are irradiated with incident energy lower and close to an absorption edge, scattering peaks appear due to an inelastic process known as resonant Raman scattering (RRS). In this process, the emitted photons have a continuous energy distribution with a high energy cut-off limit. This work presents results regarding the possibility of determining the oxidation state by resonant Raman scattering using an energy dispersive system. Pure samples of transition metals (Cu, Fe, Mn) and different oxides of them (CuO, Cu2O, Fe2O3, Mn 2O3, MnO2) were irradiated with monochromatic synchrotron radiation below their absorption edges to inspect the RRS emissions. The spectra were analyzed with specific programs using non-conventional functions for data fitting and a FFT smoothing procedure was applied. After smoothing, the RRS residuals are studied in order to detect variation with respect to the theoretical curve. These variations are closely related with the chemical environments of the absorbing element and can provide relevant structural information of the sample. The changes existing in the RRS structure between pure elements and their oxides are clearly discriminated and suggest the possibility of structural characterization by means of resonant Raman scattering using an energy-dispersive system combined with synchrotron radiation.