## photon flux $$q_{\text{p}}$$, $$\mathit{\Phi} _{\text{p}}$$

https://doi.org/10.1351/goldbook.P04636
Number of photons (quanta of radiation, $$N_{\text{p}}$$) per time interval. SI unit is $$\text{s}^{-1}$$.
Notes:
1. Mathematical definition: $$q_{\text{p}} = \text{d}N_{\text{p}}/\text{d}t$$. If the number of photons is constant over the time interval, $$q_{\text{p}} = N_{\text{p}}/t$$.
2. This quantity can be used on a @C01019@ basis by dividing the photon flux, number basis, $$q_{\text{p}}$$, by the @A00543@, the symbol then being $$q_{n\text{,p}}$$, the name 'photon flux, amount basis', SI unit is $$\text{mol s}^{-1}$$; common unit is $$\text{einstein s}^{-1}$$.
3. Although the symbol recommended by CEI is $$\mathit{\Phi} _{\text{p}}$$, the symbol $$q_{\text{p}}$$ is preferred since $$\mathit{\Phi}$$ is reserved for @Q04991@.
Source:
PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 395 [Terms] [Paper]