Term: photon number, Np
https://doi.org/10.1351/goldbook.PT07459

Definition:
Total number of photons calculated as Np = np.NA with Np the amount of photons in einsteins and NA the Avogadro constant.

Note: Mathematical definition: Np = Q/hν for monochromatic radiation of frequency ν, with Q the @R05039@.

Related Terms:
1) radiant energy (http://doi.org/10.1351/goldbook.R05039).
2) avogadro constant (http://doi.org/10.1351/goldbook.A00543).

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)

Citation: 'photon number, Np' 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.PT07459

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