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: **

*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)

- Mathematical expression: qp,λ0[1 - 10^(-A(λ))]/V on number basis, qn,p,λ0[1 - 10^(-A(λ))]/V on amount basis, where A(λ) is the @A00028@ at @W06659@ 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 @Q04991@ and using in the numerator the rate of change of the number concentration, dC/dt or the rate of change of the @A00295@, dc/dt, respectively.

PAC, 2007,