## Wikipedia - Radiant exposure (en) radiant exposure, $$H$$

https://doi.org/10.1351/goldbook.R05042
@R05039@, $$Q$$, incident from all upward directions on a small sphere divided by the cross-sectional area of that sphere. SI unit is $$\text{J m}^{-2}$$.
Notes:
1. Equivalent definition: Irradiance, $$E$$ integrated over the time of @I03255@.
2. Mathematical definition: $$H = \text{d}Q/\text{d}S = \int _{t} E\, \text{d}t$$. 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 ($$H_{\text{o}}$$, $$F_{\text{o}}$$) 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]