photon fluence rate, Ep,o

https://doi.org/10.1351/goldbook.P04635
Rate of photon fluence. Total number of photons (Np) incident from all directions on a small sphere divided by the cross-sectional area of the sphere and per time interval. SI unit is m-2 s-1. Same as photon spherical irradiance.
Notes:
  1. Mathematical definition: Ep,o = dNp/(dt dS) = dHp,o/dt . If Ep,o is constant over the time interval and the surface, Ep,o = Np/tS. Equivalent definition: Ep,o = ∫ 4π Lp ⁢dΩ with Lp the @P04639@ and Ω the solid @A00346@ of the beams passing through the given point on the surface.
  2. It reduces to @P04637@ Ep 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 @C01019@ basis by dividing Ep,o by the @A00543@, the symbol then being En,p,o, the name 'photon @FT07376-2@, amount basis', SI unit is mol m-2 s-1; common unit is einstein m-2 s-1.
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)