photon exposure, Hp

https://doi.org/10.1351/goldbook.P04632
Photon irradiance, Ep, integrated over the time of irradiation for a beam incident from all upward directions. SI unit is m−2.
Notes:
  1. Mathematical definition: Hp=∫tEpdt. If the photon irradiance is constant over the time interval, Hp=Ept.
  2. This term refers to a beam not scattered or reflected by the target or its surroundings. For a beam incident from all directions photon fluence (Hp,o, Fp,o) is an equivalent term.
  3. This quantity can be used on a chemical amount basis by dividing Hp by the Avogadro constant, the symbol then being Hn,p, the name 'photon exposure, amount basis', SI unit is molm−2; common unit is einstein m−2.
Source:
PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 394 [Terms] [Paper]
Citation: 'photon 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.P04632 RIS BibTex EndNote
Div. IIIPDFTextXMLJSONQuantity
Last revised: February 24, 2014