EXAFS radiation, reflection

The EXAFS technique but using radiation reflected at a low angle from the surface and hence giving data for the surface atomic layers (see EXAFS)... 

These examples show that EXAFS in reflection mode may provide good data on the in situ structure of even highly disordered or even amorphous anodic oxide films. It yields data for the whole film and not only of the surface and is applicable also for rough films. Therefore, it is a good alternative and complimentary to scanning probe methods like STM and AFM. However, the experimental effort with respect to equipment (synchrotron radiation source) and specimen preparation is relatively large. 

For EXAFS and particularly for XANES, data analysis is complex. The oscillation frequency/bond distance dependence means that extensive use is made of Fourier transform analysis. Most applications to date have been in the EXAFS region. In order to acquire sufficiently strong signals in a reasonable time, use has to be made of high-intensity photon fluxes, which are available at synchrotron facilities. These provide a broad-band tuneable source of high-intensity radiation, but the reduced number of facilities limits widespread dissemination of the technique. Reflection (fluorescent detection) mode is usually preferred to transmission. Experiments can be conducted in any phase, and the probing of electrode surfaces in situ is an important application. 

Surface analytical techniques. A variety of spectroscopic methods have been used to characterize the nature of adsorbed species at the solid-water interface in natural and experimental systems (Brown et al, 1999). Surface spectroscopy techniques such as extended X-ray absorption fine structure spectroscopy (EXAFS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) have been used to characterize complexes of fission products, thorium, uranium, plutonium, and uranium sorbed onto silicates, goethite, clays, and microbes (Chisholm-Brause et al, 1992, 1994 Dent et al, 1992 Combes et al, 1992 Bargar et al, 2000 Brown and Sturchio, 2002). A recent overview of the theory and applications of synchrotron radiation to the analysis of the surfaces of soils, amorphous materials, rocks, and organic matter in low-temperature geochemistry and environmental science can be found in Fenter et al (2002). 

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