Term: fluence rate, \(E_{\unicode{x26ac}}\)
https://doi.org/10.1351/goldbook.FT07376

Definition:
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:
0) 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.
1) 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.

Related Terms:
1) radiant power (http://doi.org/10.1351/goldbook.R05046).
2) angle (http://doi.org/10.1351/goldbook.A00346).
3) radiance (http://doi.org/10.1351/goldbook.R05037).
4) irradiance (http://doi.org/10.1351/goldbook.I03254).

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)

Citation: 'fluence rate, \(E_{\unicode{x26ac}}\)' 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

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