{"term":{"id":"05818","title":"spectral overlap","longtitle":"IUPAC Gold Book - spectral overlap","doi":"10.1351\/goldbook.S05818","code":"S05818","status":"current","definitions":[{"id":1,"text":"In the context of radiative energy transfer, the integral, \\(J = \\int_{0}^{\\infty} f_{\\rm{D}}^{\\prime}(\\sigma)\\ \\varepsilon_{\\rm{A}}(\\sigma) {\\rm{d}}\\sigma \\), which measures the overlap of the emission spectrum of the excited donor, D, and the absorption spectrum of the ground state acceptor, A; \\(f_{\\rm{D}}^{'}\\) is the measured normalized emission of D, \\(f_{\\rm{D}}^{'}=\\frac{f_{\\rm{D}}\\left(\\sigma \\right)}{\\int _{0}^{\\infty }f_{\\rm{D}}\\left(\\sigma \\right)  \\ \\mathrm{d}\\sigma }\\), \\(f_{\\rm{D}}(\\sigma)\\) is the photon exitance of the donor at wavenumber \\(\\sigma \\), and \\(\\varepsilon_{\\rm{A}}(\\sigma)\\) is the decadic molar absorption coefficient of A at wavenumber \\(\\sigma \\). In the context of Förster excitation transfer, \\(J\\) is given by: \\[J = \\int_{0}^{\\infty} \\frac{f_{\\rm{D}}^{^\\prime}(\\sigma)\\ \\varepsilon_{\\rm{A}}(\\sigma)}{\\sigma^{4}} {\\rm{d}}\\sigma \\] In the context of Dexter excitation transfer, \\(J\\) is given by: \\[J = \\int_{0}^{\\infty} f_{\\rm{D}}(\\sigma)\\ \\varepsilon_{\\rm{A}}(\\sigma) {\\rm{d}}\\sigma \\] In this case \\(f_{\\rm{D}}\\) and \\(\\varepsilon_{\\rm{A}}\\), the emission spectrum of donor and absorption spectrum of acceptor, respectively, are both normalized to unity, so that the rate constant for energy transfer, \\(k_{\\rm{ET}}\\), is independent of the oscillator strength of both transitions (contrast to Förster mechanism).","links":[{"term":"Dexter excitation transfer","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/D01654"},{"term":"Förster excitation transfer","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/F02488"},{"term":"absorption spectrum","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/A00043"},{"term":"emission spectrum","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/E02060"},{"term":"energy transfer","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/E02116"},{"term":"ground state","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/G02704"},{"term":"molar absorption coefficient","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/M03972"},{"term":"oscillator strength","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/O04339"},{"term":"photon exitance","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/P04631"},{"term":"radiative energy transfer","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/R05063"},{"term":"rate constant","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/O04322"}],"sources":["PAC, 1996, 68, 2223. 'Glossary of terms used in photochemistry (IUPAC Recommendations 1996)' on page 2275 (https:\/\/doi.org\/10.1351\/pac199668122223)"]}],"altoutputs":{"html":"https:\/\/goldbook.iupac.org\/terms\/view\/S05818\/html","xml":"https:\/\/goldbook.iupac.org\/terms\/view\/S05818\/xml","plain":"https:\/\/goldbook.iupac.org\/terms\/view\/S05818\/plain"},"citation":"Citation: 'spectral overlap' 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.S05818","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":"2026-06-28T17:49:48+00:00"}}