Continuous Cauchy wavelet transform analyses of EXAFS spectra: A qualitative approach

To better understand the extended x-ray absorption fine structure (EXAFS) spectroscopic information obtained for complex materials such as those encountered in Earth sciences, we propose to use the Continuous Cauchy Wavelet Transform (CCWT). Thanks to this method, the EXAFS spectra can be visualized in three-dimension: the wavevector (k), the interatomic distance uncorrected for phase-shifts (R') and the CCWT modulus (corresponding to the continuous decomposition of the EXAFS amplitude terms). Consequently, more straightforward qualitative interpretations of EXAFS spectra can be performed, even when spectral artifacts are present, such as multiple-scattering features, multi-electronic excitations or noise. More particularly, this method provides important information concerning the krange of each EXAFS contribution, such as next nearest-neighbors identification. To illustrate the potential of CCWT analyses applied to EXAFS spectra, we present first the experimental and theoretical spectra obtained for well-crystallized minerals, thorite and zircon, at the Th LIII-, and Zr K-edges, respectively. Then, we present the CCWT analyses of EXAFS spectra collected for amorphous materials of geochemical and environmental interests, including a sodium trisilicate glass and an aqueous chloride solution, at the Mo K-, and Au LIII-edges, respectively. Muñoz et al. (2002) CCWT analyses of EXAFS spectra Page 3