Second Hydration Shell Single Scattering versus First Hydration Shell Multiple Scattering in M(H2O)63+ EXAFS Spectra

Hideto Sakane, Adela Muñoz-Páez, Sofía Díaz-Moreno, José M. Martínez, Rafael R. Pappalardo, and Enrique Sánchez Marcos


The analysis of the extended X-ray absorption fine structure (EXAFS) spectra of dilute aqueous solutions (0.1 M) of Cr(NO3)3 and Rh(NO3)3 was performed using several approaches. Single- and multiple-scattering (SS and MS) phenomena were taken into account to establish the relative importance of their possible contributions to the long distance peak (R ~ 4 Å). XANADU, FEFF, and FEFFIT codes were employed to analyze the data. The first approach considered the single-scattering contribution due to the existence of a well-defined second hydration shell around both of the trivalent cations, Cr3+ and Rh3+. The second approach evaluated the contribution due to the multiple-scattering phenomena inside the first hydration shell. Comparison of experimental spectra with the calculated ones considering either one or both of the contributions led us to conclude that both contributions were significant in the high-R region of the spectra. This study supports our previous hypothesis which states that the second hydration shell structure can be obtained by EXAFS in these cations, although a quantitative analysis demands the inclusion of multiple-scattering phenomena inside the first hydration shell.

Journal of the American Chemical Society, 120 (40) 10397 - 10401 (1998).
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