Term: inner filter effect https://doi.org/10.1351/goldbook.I03047 Definition: In an emission experiment, an apparent decrease in emission quantum yield and/or distortion of bandshape as a result of reabsorption of emitted radiation. Related Terms: 1) quantum yield (http://doi.org/10.1351/goldbook.Q04991). Source: Citation: 'inner filter effect' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.I03047 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. 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.