Can someone tell me if quantum yield of a reaction factors in the number of electrons needed to create the particular species? If not, is there a metric that does?
For example, I have a 4 electron reduction which means that even if I have 100% efficiency, my quantum yield is
$$\frac{\text{# molecules reduced}}{\text{# photons absorbed}} = 0.25$$
Is there a better metric I can use so that 1.0 will be 100% efficiency?
I'm not aware of a definition of quantum yield that factors the electrons in. The normative reference was/is Silvia Braslavsky's Glossary of terms used in photochemistry (SRC).
Unless I misunderstood, you do have an overall four electron reduction, but this happens in a sequence of four excitation events.
From a formal point of view, the quantum yield(s) should be given for each of these processes. I reckon that this isn't possible, so an overall quantum yield of 0.25 is all you can get. In the end, I'd simply explain that, rather that looking for some "tricks" to come up with a more impressive number.
