radiant exposure, \(H\)

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.
  1. Equivalent definition: Irradiance, E integrated over the time of @I03255@.
  2. Mathematical definition: H = dQ/dS = ∫(t) E.dt. If Q is constant over the area, H = Q/S. If E is constant over the time interval, H = E.t.
  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.
PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 409 (https://doi.org/10.1351/pac200779030293)