Extended X-ray absorption fine structure

<p>Extended X-ray absorption fine structure (EXAFS), along with X-ray absorption near edge structure (<a href="/facts/XANES/sl9mpCrk">XANES</a>), is a subset of X-ray absorption spectroscopy (<a href="/facts/X-ray_absorption_spectroscopy/y5lvDjr4">XAS</a>). Like other <a href="/facts/Absorption_spectroscopy/GH7RC14D">absorption spectroscopies</a>, XAS techniques follow <a href="/facts/Beer%25E2%2580%2593Lambert_law/nl64rI1C">Beer's law</a>. The <a href="/facts/X-ray/wseP79cN">X-ray</a> <a href="/facts/Absorption_coefficient/ppCIsSGw">absorption coefficient</a> of a material as a function of energy is obtained by directing X-rays of a narrow energy range at a sample, while recording the incident and transmitted x-ray intensity, as the incident x-ray energy is incremented.
</p><p>When the incident x-ray energy matches the <a href="/facts/Binding_energy/2Q3poXgg">binding energy</a> of an <a href="/facts/Electron/L0KBo5cW">electron</a> of an atom within the sample, the number of x-rays absorbed by the sample increases dramatically, causing a drop in the transmitted x-ray intensity. This results in an absorption edge. Every element has a set of unique absorption edges corresponding to different binding energies of its electrons, giving XAS element selectivity. XAS spectra are most often collected at <a href="/facts/Synchrotron/J1oWBgbU">synchrotrons</a> because the high intensity of synchrotron X-ray sources allows the concentration of the absorbing element to reach as low as a few parts per million. Absorption would be undetectable if the source were too weak. Because X-rays are highly penetrating, XAS samples can be gases, solids or liquids.
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Extended X-ray absorption fine structure open-in-new

Extended X-ray absorption fine structure