Caption
Blue lines in Figure (b) describe the correct radial structure function, N(R), as determined by the structure of the material. The N(R) has radial components (the number of coordinating atoms) at sparse interatomic distance R. As the distance increase, the N(R) increases the number of atoms (intensity of N(R)) coordinating at the same distance owing to the structural symmetry of substances. In contrary to such discrete N(R), we have obtained information about the microstructure from a green spectrum in Figure (a), which is calculated by Fourier transformation of the EXAFS oscillation spectrum (right side of figure). This spectrum is a continuous function of the interatomic distance R, and shows the intensity decreasing as R increases. This means that as the atomic distance increases, this method cannot correctly estimate the radial structure function of coordinating atoms.
Adapted from: Akai, I., Iwamitsu, K., Igarashi, Y., Okada, M., Setoyama, H., Okajima, T., & Hirai, Y. (2018). Sparse Modeling of an Extended X-Ray Absorption Fine-Structure Spectrum Based on a Single-Scattering Formalism. Journal of the Physical Society of Japan, 87(7), 074003. doi:10.7566/jpsj.87.074003