fluence rate, E⚬ 

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:
  1. Mathematical definition: Eo=dPdS=dHodt. If the radiant power is constant over the area S, Eo=PS. Equivalent definition: Eo=∫4πLdΩ, with Ω the solid angle of each beam passing through the given point on the surface and L the radiance of the beam at that point.
  2. Fluence rate is identical to spherical irradiance and reduces to irradiance, E, for a parallel and perpendicularly incident beam not scattered or reflected by the target or its surroundings.
Source:
PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 340 [Terms] [Paper]
Citation: 'fluence rate' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.FT07376 RIS BibTex EndNote
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Last revised: February 24, 2014