https://doi.org/10.1351/goldbook.Q04991

Number of defined events occurring per __photon absorbed__ by the system.

The integral quantum yield is \[\mathit{\Phi}(\lambda) = \frac{\text{number of events}}{\text{number of photons absorbed}}\] For a photochemical reaction, \[\mathit{\Phi}(\lambda) = \frac{\text{amount of reactant consumed or product formed}}{\text{number of photons absorbed}}\] The differential quantum yield is \[\mathit{\Phi}(\lambda) = \frac{\text{d}x/\text{d}t}{q_{n,\text{p}}^{0}[ 1 - 10^{-A(\lambda)} ]}\] where dx/dt is the rate of change of a measurable quantity (spectral or any other property), and qn,p0 the amount of photons (mol or its equivalent einstein) - Strictly, the term quantum yield applies only for monochromatic excitation. Thus, for the differential quantum yield, the absorbed spectral photon flux density (number basis or amount basis) should be used in the denominator of the equation above when x is either the number concentration (C = N / V), or the @A00295@ (c), respectively.
- Φ can be used for @P04647@ (such as, e.g., @I03123@, @F02453@ and @P04569@) or photochemical reactions.

PAC, 2007,