In the field of photoredox catalysis, it is important to understand which compound in the complex reaction mixture reacts with the excited state of the photocatalyst, and for this reason so-called luminescence quenching experiments are often an integral part of any mechanistic work. In such studies, the luminescence intensity of the photocatalyst is probed under varying concentrations of the quencher compound, and the results are plotted using the Stern-Volmer plot, generally obtaining a linear relationship for well-behaved dynamically quenched systems when utilizing photocatalysts with a single (emissive) excited state, according to equation 6.