Term: photon fluence, Hp,o, \(F_{\text{p,o}}\)
https://doi.org/10.1351/goldbook.P04634

Definition:
Amount of photons (quanta of radiation) incident on a small sphere from all directions, divided by the cross-sectional area of that sphere and integrated over time. Photons per surface area (quanta m-2). SI unit is m-2.

Notes:
0) Mathematical definition: Hp,o = Fp,o = dNp/dS = ∫(t) Ep,o.dt with Ep,o the @P04635@, integrated over the duration of the @I03255@, t. If Ep,o is constant over the time interval, Hp,o = Fp,o = Ep,o.t.
1) This quantity can be used on a @C01019@ basis by dividing Hp,o by the @A00543@, the symbol then being Hn,p,o, the name 'photon fluence, amount basis', SI unit is mol m-2; common unit is einstein m-2.

Related Terms:
1) photon fluence rate (http://doi.org/10.1351/goldbook.P04635).
2) irradiation (http://doi.org/10.1351/goldbook.I03255).
3) chemical amount (http://doi.org/10.1351/goldbook.C01019).
4) 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 395 (https://doi.org/10.1351/pac200779030293)

Citation: 'photon fluence, Hp,o, \(F_{\text{p,o}}\)' 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.P04634

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