https://doi.org/10.1351/goldbook.P04632
Photon irradiance, \(E_{\rm{p}}\), integrated over the time of irradiation for a beam incident from all upward directions. SI unit is \(\rm{m}^{-2}\).
Notes:
- Mathematical definition: \(H_{\rm{p}} = \int_{t}E_{\rm{p}}\rm{d}t\). If the photon irradiance is constant over the time interval, \(H_{\rm{p}} = E_{\rm{p}}t\).
- 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 (\(H_{\rm{p,o}}\), \(F_{\rm{p,o}}\)) is an equivalent term.
- This quantity can be used on a chemical amount basis by dividing \(H_{\rm{p}}\) by the Avogadro constant, the symbol then being \(H_{n\rm{,p}}\), the name 'photon exposure, amount basis', SI unit is \(\pu{mol m-2}\); common unit is \(\pu{einstein m-2}\).