## photon fluence rate, $$E_{\text{p,o}}$$

https://doi.org/10.1351/goldbook.P04635
Rate of photon fluence. Total number of photons ($$N_{\text{p}}$$) incident from all directions on a small sphere divided by the cross-sectional area of the sphere and per time interval. SI unit is $$\text{m}^{-2}\ \text{s}^{-1}$$. Same as photon @[email protected]
Notes:
1. Mathematical definition: $$E_{\text{p,o}} = \text{d}N_{\text{p}}/\left ( \text{d}t\, \text{d}S \right ) = \text{d}H_{\text{p,o}}/\text{d}t$$. If $$E_{\text{p,o}}$$ is constant over the time interval and the surface, $$E_{\text{p,o}} = N_{\text{p}}/t\, S$$. Equivalent definition: $$E_{\text{p,o}} = \int _{4\pi}L_{\text{p}}\text{d}\varOmega$$ with $$L_{\text{p}}$$ the @[email protected] and $$\varOmega$$ the solid @[email protected] of the beams passing through the given point on the surface.
2. It reduces to @[email protected] $$E_{\text{p}}$$ for a parallel and normally incident beam not scattered or reflected by the target or its surroundings.
3. This quantity can be used on a @[email protected] basis by dividing $$E_{\text{p,o}}$$ by the @[email protected], the symbol then being $$E_{n\text{,p,o}}$$, the name 'photon @[email protected], amount basis', SI unit is $$\text{mol m}^{-2}\ \text{s}^{-1}$$; common unit is $$\text{einstein m}^{-2}\ \text{s}^{-1}$$.
Source:
PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 395 [Terms] [Paper]