Multiple-scattering regime and higher-order correlations in x-ray-absorption spectra of liquid solutions

M. Benfatto, C. R. Natoli, A. Bianconi, J. Garcia, A. Marcelli, M. Fanfoni, and I. Davoli
Phys. Rev. B 34, 5774 – Published 15 October 1986
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Abstract

By making a comparison between the Mn K-edge absorption of (MnO4) and [Mn(H2O)6]2+ complexes in aqueous solution we obtain an experimental determination of the energy extent of the type-II multiple-scattering (MS) regime that is substantially wider than expected. Theoretical calculations based on the MS formalism support this conclusion. We also recognize three energy regions in the absorption spectra of these complexes: a full MS region, where numerous or an infinite number of MS paths of high order contribute (depending on whether the MS series converges or not), an intermediate MS region, where only a few MS paths of low order are relevant, and a single-scattering region where the photoelectron is backscattered only once by the ligands [extended x-ray-absorption fine-structure (EXAFS) regime]. Theoretical considerations show that this must be a general situation in x-ray-absorption spectra and opens the way to a unified scheme for their interpretation. The energy extent of the three regions is obviously system dependent. We also show how to generalize to MS contributions the usual EXAFS analysis using curved-wave propagators and indicate how to extract geometrical information from the spectra of the two clusters investigated. In particular the method is used to derive the MnOOMn path length in the (MnO4) complex.

  • Received 12 May 1986

DOI:https://doi.org/10.1103/PhysRevB.34.5774

©1986 American Physical Society

Authors & Affiliations

M. Benfatto and C. R. Natoli

  • Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, Casella Postale 13, I-00044 Frascati (Roma), Italy

A. Bianconi, J. Garcia, A. Marcelli, and M. Fanfoni

  • Dipartimento di Fisica, Università degli Studi di Roma ‘‘La Sapienza,’’ I-00185 Roma, Italy

I. Davoli

  • Dipartimento di Matematica e Fisica, Università degli Studi di Camerino, I-62032 Camerino, Italy

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Vol. 34, Iss. 8 — 15 October 1986

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