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 @FT07376-1@.
Notes:
- 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 @P04639@ and \(\varOmega\) the solid @A00346@ of the beams passing through the given point on the surface.
- It reduces to @P04637@ \(E_{\text{p}}\) for a parallel and normally incident beam not scattered or reflected by the target or its surroundings.
- This quantity can be used on a @C01019@ basis by dividing \(E_{\text{p,o}}\) by the @A00543@, the symbol then being \(E_{n\text{,p,o}}\), the name 'photon @FT07376-2@, amount basis', SI unit is \(\pu{mol m-2 s-1}\); common unit is \(\text{einstein m}^{-2}\ \text{s}^{-1}\).