https://doi.org/10.1351/goldbook.P04634
Amount of photons (quanta of radiation) incident on a small sphere from all directions, divided by the cross-sectional area of that sphere and integrated over time. Photons per surface area (\(\rm{quanta m}^{-2}\)). SI unit is \(\rm{m}^{-2}\).
Notes:
- Mathematical definition: \(H_{\rm{p,o}} = F_{\rm{p,o}} = \rm{d}N_{\rm{p}}/\rm{d}S = \int_{t}E_{\rm{p,o}}\rm{d}t\) with \(E_{\rm{p,o}}\) the photon fluence rate, integrated over the duration of the irradiation, \(t\). If \(E_{\rm{p,o}}\) is constant over the time interval, \(H_{\rm{p,o}} = F_{\rm{p,o}} = E_{\rm{p,o}}\,t\).
- This quantity can be used on a chemical amount basis by dividing \(H_{\rm{p,o}}\) by the Avogadro constant, the symbol then being \(H_{n\rm{,p,o}}\), the name 'photon fluence, amount basis', SI unit is \(\pu{mol m-2}\); common unit is \(\pu{einstein m-2}\).