Polariton-exciton effects can also be probed using the energy gap law (Equation ), whereby cavity coupling to the system of interest is the dominant mechanism, and all other internal conversion mechanisms are higher-order processes . This casts the rate constant in terms of the final dark state and numerous saddle-point approximations : where subscripts LP and UP refer to the lower and upper polaritonic states respectively, and X is the number of molecules in the cavity. Assuming a continuum of dark states with discrete polaritonic states, or that the majority of the system energy is distributed through dark modes, internal conversion should be dominant. While this was tested on an arbitrary system by Poh and co-workers , tuning was shown to be instrumental in its control.