Wavelet analysis of extended x-ray absorption fine structure data

Extended x-ray absorption fine structure data evaluation usually begins with the Fourier transform of the spectrum. We suggest the wavelet transform as a complement to the Fourier transform. While the Fourier transform analyzes the distances to the backscattering atoms, wavelet transform additionally reveals the wavenumber dependence of the scattering. Thus wavelet analysis can differentiate between heavier and lighter backscattering atoms, even if they are almost equidistant from the central atom. First the method of operation and the advantage of the wavelet analysis will be demonstrated by simple models. Then it is applied to the interpretation of extended x-ray absorption fine structure spectra concerning the complexation of Uranium(VI) with the carboxylic groups acetic-, formic-, and glycolic acid. The wavelet transform analysis suggests clearly for the system Uranium-formic acid both, U-U and U-C-C, structural elements. In contrast to the clear separation of different scattering paths by wavelet transform, Fourier transform analysis was not able to resolve the two different backscattering processes.