Figure 4.

(a) Backscattering amplitude factors associated with the elements present in the system under study. Moduli of EXAFS WTs magnified in the 2–4 Å R-space range for the following reaction steps: (b) step 1, pretreatment in O₂; (c) step 2, reduction in NO/NH₃/He; (d) step 3, oxidation in 10% O₂/He; (e) step 4, exposure to NO/He or (f) step 4′, exposure to NH₃/He. For all the WTs a common intensity scale is employed. Part (d) also shows the corresponding EXAFS spectra in k-space and R-space (conventional FT) in the relevant ranges, as well as the k-space range characteristic of low-Z (O/N, Si/Al) and high-Z scatterers (Cu). All spectra measured at 200 °C.