Term: self-absorption factor https://doi.org/10.1351/goldbook.S05581 Definition: The ratio between the quantity of the radiation emitted by the source and the quantity of the radiation as produced by the radioactive nuclei present in the source. Synonymous with source efficiency. Related Terms: 1) radioactive (http://doi.org/10.1351/goldbook.R05077). Source: PAC, 1994, 66, 2513. 'Nomenclature for radioanalytical chemistry (IUPAC Recommendations 1994)' on page 2525 (https://doi.org/10.1351/pac199466122513) Citation: 'self-absorption factor' 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.S05581 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.