## absorbed (spectral) photon flux density

https://doi.org/10.1351/goldbook.AT07312
Number of photons of a particular @W06659@ per time interval (@S05821@, number basis, $$q_{\text{p},\lambda }$$, or @S05821@, amount basis, $$q_{n,\text{p},\lambda }$$) absorbed by a system per volume, $$V$$. On number basis, SI unit is $$\text{s}^{-1}\ \text{m}^{-4}$$, and the common unit is $$\text{s}^{-1}\ \text{cm}^{-3}\ \text{nm}^{-1}$$. On amount basis, SI unit is $$\text{mol s}^{-1}\ \text{m}^{-4}$$, and a common unit is $$\text{einstein}\ \text{s}^{-1}\ \text{cm}^{-3}\ \text{nm}^{-1}$$.
Notes:
1. 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 @A00028@ at @W06659@ $$λ$$ and superscript $$0$$ (zero) indicates incident photons.
2. Absorbed spectral photon flux density (number basis or amount basis) should be used in the denominator when calculating a differential @Q04991@ and using in the numerator the rate of change of the number concentration, $$\frac{dC}{dt}$$ or the rate of change of the @A00295@, $$\frac{dc}{dt}$$, respectively.
Source:
PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 297 [Terms] [Paper]