where TIPS-Tn 8 mM lation, the maximum amount the ground-state population could change in the singlet lifetime was <1%, so the ground-state concentration was treated as a constant ([S 0 ] = 8 mM). The ISC rate constant, k ISC , was initially assumed to be negligible compared with the pseudo-first-order rate constant of SF at this concentration, k SF [S 0 ], and was set to zero. Singlet-singlet annihilation was ignored since there was no power dependence at the excitation powers used here (supplementary material Fig. ). Triplet-triplet annihilation or triplet fusion was also ignored.