photon fluence rate, E p , o
Rate of photon fluence. Total number of photons (N 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 m −2 s −1. Same as photon spherical irradiance.
  1. Mathematical definition: E p , o = d N p / d t d S = d H p , o / d t. If E p , o is constant over the time interval and the surface, E p , o = N p / t S Equivalent definition: E p , o = ∫ 4 π L p ⁢ d Ω with L p the photon radiance and Ω the solid angle of the beams passing through the given point on the surface.
  2. It reduces to photon irradianceE 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 chemical amount basis by dividing E p , o by the Avogadro constant, the symbol then being E n , p , o, the name 'photon fluence rate, amount basis', SI unit is mol m −2 s −1; common unit is einstein m −2 s −1.
PAC, 2007, 79, 293 (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 395