https://doi.org/10.1351/goldbook.AT07312
Number of photons of a particular wavelength per time interval (spectral photon flux, number basis, \(q_{\rm{p},\lambda }\), or spectral photon flux, amount basis, \(q_{n,\rm{p},\lambda }\)) absorbed by a system per volume, \(V\). On number basis, SI unit is \(\rm{s}^{-1}\ \rm{m}^{-4}\), and the common unit is \(\rm{s}^{-1}\ \rm{cm}^{-3}\ \rm{nm}^{-1}\). On amount basis, SI unit is \(\pu{mol s-1 m-4}\), and a common unit is \(\pu{einstein s-1 cm-3 nm-1}\).
Notes:
- Mathematical expression: \(\frac{q_{p,\lambda }^{0}[1 - 10^{-A(\lambda )} ]}{V}\) on number basis, \(\frac{q_{n,p,\lambda }^{0}[ 1 - 10^{-A(\lambda )} ]}{V}\) on amount basis, where \(A(λ)\) is the absorbance at wavelength \(λ\) and superscript \(0\) (zero) indicates incident photons.
- Absorbed spectral photon flux density (number basis or amount basis) should be used in the denominator when calculating a differential quantum yield and using in the numerator the rate of change of the number concentration, \(\frac{dC}{dt}\) or the rate of change of the amount concentration, \(\frac{dc}{dt}\), respectively.