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 m2.
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 molm2; common unit is einstein m2.
Source:
PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 394 [Terms] [Paper]