absorbed (spectral) photon flux density

https://doi.org/10.1351/goldbook.AT07312
Number of photons of a particular wavelength per time interval (spectral photon flux, number basis, qp,λ, or spectral photon flux, amount basis, qn,p,λ) absorbed by a system per volume, V. On number basis, SI unit is s-1 m-4, and the common unit is s-1 cm-3 nm-1. On amount basis, SI unit is mol s-1 m-4, and a common unit is einstein s-1 cm-3 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 (https://doi.org/10.1351/pac200779030293)