{"term":{"id":"08224","title":"apodization","longtitle":"IUPAC Gold Book - apodization","doi":"10.1351\/goldbook.08224","code":"08224","status":"current","definitions":[{"id":1,"text":"Technical term for changing the shape of a mathematical function, electrical signal, or optical transmission to remove or smooth a discontinuity at the edges, literally meaning 'removing the foot'.","notes":{"1":"Originally, 'apodization' described the procedure by which Fourier-transform infrared spectra are corrected for the side lobes that appear in the wings of spectral bands when the interferogram is not zero at its limits, by multiplying the interferogram prior to Fourier transformation by a weighting function that is zero at its limits (see Fourier-transform spectroscopy). Its use has broadened in recent years to include weighting functions that are not zero at their limits.","2":"Apodization is also used for manipulating FIDs (free induction decay) to enhance specific components of the signal, for example to improve signal-to-noise or resolution, and is achieved by application of specific shapes to the FID, e.g., in nuclear magnetic resonance spectroscopy: exponential, Gaussian or sine-bell; in infrared spectroscopy: Boxcar, Happ-Genzel, Norton-Beer, cosine."},"links":[{"term":"free induction decay","url":"https:\/\/goldbook.iupac.org\/terms\/view\/08249"},{"term":"infrared spectroscopy","url":"https:\/\/goldbook.iupac.org\/terms\/view\/08618"},{"term":"nuclear magnetic resonance spectroscopy","url":"https:\/\/goldbook.iupac.org\/terms\/view\/08218"},{"term":"signal-to-noise","url":"https:\/\/goldbook.iupac.org\/terms\/view\/08282"},{"term":"spectral bands","url":"https:\/\/goldbook.iupac.org\/terms\/view\/08285"}],"sources":["PAC, 2021, 93, 647. 'Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)' on page 651 (https:\/\/doi.org\/10.1515\/pac-2019-0203)"]}],"altoutputs":{"html":"https:\/\/goldbook.iupac.org\/terms\/view\/08224\/html","xml":"https:\/\/goldbook.iupac.org\/terms\/view\/08224\/xml","plain":"https:\/\/goldbook.iupac.org\/terms\/view\/08224\/plain"},"citation":"Citation: 'apodization' 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.08224","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":"2026-06-30T23:33:59+00:00"}}