Title: photon number
Long Title: IUPAC Gold Book - photon number
DOI: 10.1351/goldbook.PT07459
Status: current
Index: quantity

Definition
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.

Note
Mathematical definition: \(N_{\rm{p}} = Q/h\nu\) for monochromatic radiation of frequency \(\nu\), with \(Q\) the radiant energy.

Related Terms
- Avogadro constant: https://goldbook.iupac.org/terms/view/A00543
- radiant energy: https://goldbook.iupac.org/terms/view/R05039

Source
- PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 396 (https://doi.org/10.1351/pac200779030293)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/PT07459/html
- json: https://goldbook.iupac.org/terms/view/PT07459/json
- xml: https://goldbook.iupac.org/terms/view/PT07459/xml

Citation: 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
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Accessed: 2026-07-29T17:49:43+00:00