{"term":{"id":"08249","title":"free induction decay","longtitle":"IUPAC Gold Book - free induction decay","doi":"10.1351\/goldbook.08249","code":"08249","status":"current","initialism":"<em>initialism<\/em>: FID","definitions":[{"id":1,"text":"Indication from a pulsed spectroscopy experiment that takes the form of damped sine waves arising from the excited system returning to equilibrium.","notes":{"1":"In nuclear magnetic resonance spectroscopy, the FID consists of sine waves oscillating at the Larmor angular frequency (\\(\\omega\\)) and dampened by net dephasing time relaxation (\\(T_{2}^{*}\\)), \\(\\sin (\\omega t) \\exp(-t\/T_{2}^{*})\\)."},"links":[{"term":"Larmor angular frequency","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/08375"},{"term":"net dephasing time","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/08380"},{"term":"nuclear magnetic resonance spectroscopy","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/08218"}],"sources":["PAC, 2021, 93, 647. 'Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)' on page 659 (https:\/\/doi.org\/10.1515\/pac-2019-0203)"]}],"altoutputs":{"html":"https:\/\/goldbook.iupac.org\/terms\/view\/08249\/html","xml":"https:\/\/goldbook.iupac.org\/terms\/view\/08249\/xml","plain":"https:\/\/goldbook.iupac.org\/terms\/view\/08249\/plain"},"citation":"Citation: 'free induction decay' 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.08249","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":"2026-05-28T11:13:36+00:00"}}