photon fluence, Hp,o, Fp,o 

https://doi.org/10.1351/goldbook.P04634
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:
  1. Mathematical definition: Hp,o=Fp,o=dNp/dS=∫tEp,odt with Ep,o the photon fluence rate, integrated over the duration of the irradiation, t. If Ep,o is constant over the time interval, Hp,o=Fp,o=Ep,ot.
  2. This quantity can be used on a chemical amount basis by dividing Hp,o by the Avogadro constant, the symbol then being Hn,p,o, the name 'photon fluence, amount basis', SI unit is molm−2; common unit is einstein m−2.
Source:
PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 395 [Terms] [Paper]
Citation: 'photon fluence' 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 RIS BibTex EndNote
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Last revised: February 24, 2014