Also contains definitions of: radiant energy fluence rate, spherical irradiance

https://doi.org/10.1351/goldbook.FT07376

Total radiant power, P, incident from __all directions__ onto a small sphere divided by the cross-sectional area of that sphere. SI unit is W m-2.**Notes: **

*Source: *

PAC, 2007,*79*, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 340 (https://doi.org/10.1351/pac200779030293)

- Mathematical definition: Eo = dP/dS = dHo/dt. If the @R05046@ is constant over the area S, Eo = P/S. Equivalent definition: Eo = ∫ 4.π.L dΩ, with Ω the solid @A00346@ of each beam passing through the given point on the surface and L the @R05037@ of the beam at that point.
- Fluence rate is identical to spherical irradiance and reduces to @I03254@, E, for a parallel and perpendicularly incident beam
__not scattered or reflected__by the target or its surroundings.

PAC, 2007,