radiant exposure, H 

https://doi.org/10.1351/goldbook.R05042
Radiant energy, Q, incident from all upward directions on a small sphere divided by the cross-sectional area of that sphere. SI unit is J m−2.
Notes:
  1. Equivalent definition: Irradiance, E integrated over the time of irradiation.
  2. Mathematical definition: H=dQ/dS=∫tEdt. If Q is constant over the area, H=Q/S. If E is constant over the time interval, H=Et.
  3. This term refers to a beam not scattered or reflected by the target or its surroundings. For a beam incident from all directions fluence (Ho, Fo) is an equivalent term.
Source:
PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 409 [Terms] [Paper]
Citation: 'radiant exposure' 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.R05042 RIS BibTex EndNote
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Last revised: February 24, 2014