{"term":{"id":"09212","title":"X-ray absorption fine structure spectroscopy","longtitle":"IUPAC Gold Book - X-ray absorption fine structure spectroscopy","doi":"10.1351\/goldbook.09212","code":"09212","status":"current","synonym":"<em>synonym<\/em>: XAFS","definitions":[{"id":1,"text":"Measurement method to measure the absorption of X-rays at energies near and above (typically several hundred \\(\\pu{eV}\\) greater) an absorption edge, over which fine structure (modulation of the X-ray absorption coefficient) can be detected.","notes":{"1":"XAFS includes both extended X-ray absorption fine structure spectroscopy and X-ray absorption near-edge spectroscopy. It involves transitions from a core-level to an unoccupied orbital or band and mainly reflects the local atomic structure and bonding (SEXAFS) and the density of the unoccupied electronic states (XANES).","2":"XAFS measurements usually start some \\(\\pu{10 eV}\\) before the core-level binding energy (the absorption edge) of the emitting atoms, because in many cases pre-edge features are used to identify chemical bonds [example: \\(\\uppi^{\\ast}\\) resonances (excitation into lowest unoccupied molecular orbitals) in C K-edge spectra of polymer samples].","3":"Usefully sharp absorption edges are commonly observed in X-ray absorption spectra, although broader increases can be observed for some inner-shell excitations with short lifetimes.","4":"XAFS spectra are best recorded when a highly intense beam of X-rays from a synchrotron is used along with a high resolution double crystal or curved crystal spectrometer. Detectors include ionization chambers, scintillation counters, and solid state detectors."},"links":[{"term":"X-ray absorption near-edge spectroscopy","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/09213"},{"term":"extended X-ray absorption fine structure spectroscopy","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/09198"}],"sources":["PAC, 2020, 92, 1781. 'Glossary of methods and terms used in surface chemical analysis (IUPAC Recommendations 2020)' on page 1794 (https:\/\/doi.org\/10.1515\/pac-2019-0404)"]}],"altoutputs":{"html":"https:\/\/goldbook.iupac.org\/terms\/view\/09212\/html","xml":"https:\/\/goldbook.iupac.org\/terms\/view\/09212\/xml","plain":"https:\/\/goldbook.iupac.org\/terms\/view\/09212\/plain"},"citation":"Citation: 'X-ray absorption fine structure spectroscopy' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351\/goldbook.09212","license":"The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/) for individual terms.","collection":"If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org .","disclaimer":"The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.","accessed":"2026-05-18T04:28:50+00:00"}}