07459 IUPAC Gold Book - photon number 10.1351/goldbook.PT07459 PT07459 current quantity 1 Total number of photons calculated as \(N_{\rm{p}} = n_{\rm{p}}\, N_{\rm{A}}\) with \(N_{\rm{p}}\) the amount of photons in einsteins and \(N_{\rm{A}}\) the Avogadro constant. Mathematical definition: \(N_{\rm{p}} = Q/h\nu\) for monochromatic radiation of frequency \(\nu\), with \(Q\) the radiant energy. Avogadro constant https://goldbook.iupac.org//terms/view/A00543 radiant energy https://goldbook.iupac.org//terms/view/R05039 PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 396 (https://doi.org/10.1351/pac200779030293) https://goldbook.iupac.org/terms/view/PT07459/html https://goldbook.iupac.org/terms/view/PT07459/json https://goldbook.iupac.org/terms/view/PT07459/plain Citation: 'photon number' 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.PT07459 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. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . 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. 2026-05-09T09:35:19+00:00