\b[The phosphorescence quantum yield is the number of phosphorescence photons emitted per photon absorbed.] In rate form,
$$
\phi_P=\frac{\text{rate of phosphorescence photon emission}}{\text{rate of photon absorption}}=\frac{k_P[T_1]}{I_{\rm abs}}.
$$
It is dimensionless. The denominator counts absorbed photons, not incident photons or the instantaneous triplet population.


Solution

Past exam of the chemistry course of the year 3 of the natural sciences course of the University of Cambridge / 2021 / Paper 2A / Section B / 22 / b / i / Solution

 Solution (source code)