The Historical Development of X-ray Absorption Fine Spectroscopy and of Its Applications to Materials Science

Abstract

Abstract. This essay sketches the development of X-ray Absorption Fine Spectroscopy (XAFS) ever since the second half of 20 th century. At that time, synchrotrons started competing with X-ray discharge tubes as the sources of the excitation able to show the pre-and near-edge structures (XANES) and extended oscillations (EXAFS) that characterize the X-ray absorption edge of solid matter. Actually, modern XAFS began after 1975, when the hard-X-ray synchrotron radiation derived from storage rings took over. Ever since, XAFS greatly contributed to both technical refinement and to theoretical development of Materials Science. Although a unified theory of X-ray fine absorption has not been reached yet, many XAFS advancements benefited of theoretical models and complex calculations made possible by the continuous growth of the computing power, while contributing to developing new or previously never used materials.

In Situ Kinetic Observations on Crystal Nucleation and Growth

“…EXAFS characterizes the oscillatory variations of the X-ray absorption in ∼30–1000 eV. By measuring the constructive and destructive interference of the emitted electrons as a function of energy, the information on the number, type, as well as distances of the neighboring atoms could be obtained from the spectrum . Meanwhile, different from diffraction methods (sensitive to long-range ordered structure), the EXAFS method is element specific and sensitive to the oxidation state and local (fine) structure with short-range order. , Hence, EXAFS is suitable for the characterization of liquid solutions, disordered materials, amorphous and crystalline samples, and is critical for probing the chemical environments at the initial crystal nucleation stages in various material systems.…”

“…36 In 1913, de Broglie measured the first absorption edges of Ag and Br K-edges. 224 Nevertheless, practical applications require more brilliant polychromatic X-ray sources, better detectors, and advanced theory to interpret the obtained signals. For this reason, the advances in EXAFS coincides with that of synchrotron light sources for a long time.…”

“…EXAFS is a very powerful analytical tool which utilizes a final state interference effect involving scattering of the outgoing photoelectron from the neighboring atoms to probe the local geometric and chemical structure around a given atomic species . In 1913, de Broglie measured the first absorption edges of Ag and Br K-edges . Nevertheless, practical applications require more brilliant polychromatic X-ray sources, better detectors, and advanced theory to interpret the obtained signals.…”

Structure-Redox Response Correlation in a Few Select Heme Systems Using X-ray Absorption Spectroelectrochemistry

“…X-ray absorption spectroscopy (XAS) is a nondestructive technique for probing local electronic structure around inorganic and organic/biological metal scaffolds. , Fe K-edge XAS has been important in identifying different functional states of hemes. , The difference between the functional forms of oxygen binding globins and redox heme enzymes, as well as redox induced structural changes in these systems, has been studied using XAS. , Subtle structural differences, such as between a protein in crystalline form and in solution (functional) form, can also be resolved through XAS. , …”

“…inorganic and organic/biological metal scaffolds. 12,13 Fe Kedge XAS has been important in identifying different functional states of hemes. 14,15 The difference between the functional forms of oxygen binding globins and redox heme enzymes, as well as redox induced structural changes in these systems, has been studied using XAS.…”