## photon fluence, $$H_{\text{p,o}}$$, $$F_{\text{p,o}}$$

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: $$H_{\text{p,o}} = F_{\text{p,o}} = \text{d}N_{\text{p}}/\text{d}S = \int_{t}E_{\text{p,o}}\text{d}t$$ with $$E_{\text{p,o}}$$ the @P04635@, integrated over the duration of the @I03255@, $$t$$. If $$E_{\text{p,o}}$$ is constant over the time interval, $$H_{\text{p,o}} = F_{\text{p,o}} = E_{\text{p,o}}\,t$$.
2. This quantity can be used on a @C01019@ basis by dividing $$H_{\text{p,o}}$$ by the @A00543@, the symbol then being $$H_{n\text{,p,o}}$$, the name 'photon fluence, amount basis', SI unit is $$\text{mol m}^{-2}$$; common unit is $$\text{einstein m}^{-2}$$.
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)