Continuous Cauchy Wavelet Transform of XAFS Spectra

The continuous Cauchy wavelet transform (CCWT) is applied to the analysis of XAFS spectra. Thanks to that method, XANES and EXAFS signals can be visualized in threedimension: the wavevector (k), the interatomic distance uncorrected for phase-shifts (R') and the CCWT modulus (corresponding to the continuous decomposition of the amplitude terms). Applied to EXAFS spectra, the CCWT analysis provides straightforward qualitative information related to the k-range of each “R'-EXAFS” contribution. Such information is particularly useful to perform next nearest-neighbors identification, despite the presence of spectral artifacts such as multiple-scattering features, multi-electronic excitations or noise. When applied to XANES spectra, the CCWT analysis helps highly to measure the “spectral limit” between XANES and EXAFS regions, as well as the energy range required to model properly next-nearest neighbors. To further illustrate the potential of CCWT analyses applied to XAFS spectra, we present examples related to: (1) a XANES spectrum collected at the Ti K-edge for titanite (CaTiSiO5); (2) an experimental Au LIII-edge EXAFS spectrum for gold sorbed on goethite (FeO(OH)).