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