where W system is the rate constant for the system of interest, be it chromophore, quantum dot, thin film, etc., and W cavity is the internal conversion rate constant within an electromagnetic vacuum. Tsai and co-workers used the formalism used by Lin (Equation ), however as per the separability between the system rate and cavity interaction in Equation , any method should be applicable. In particular, the two rate components can be calculated, and readily compared, with the only free parameter being the effective mode volume. Previous studies have shown that the use of Fermi's Golden rule (Equation ), even in the strong-coupling regime with in a cavity, is applicable. Finally, W cavity can be expressed in full as :