used. Substituting this ISC rate into the SF model described by Eqs. ( ) and ( ) leads to 17% T 1 production for a singlet lifetime of 18 ns and 13% T 1 for a lifetime of 13 ns (Table ). This amount of triplet formation was absent in their experimental data, so this ISC rate is unfeasibly fast. Note that the T 1 lifetime used does affect the predicted T 1 yield on a microsecond time scale, so we have used the 6.7 µs reported by Walker et al., which is already much shorter than other estimates (Table ). The T 1 lifetime would have to be as short as 100 ns to begin to approach undetectable T 1 levels. If we instead use the upper limit of the ISC rate constant found here, a triplet yield of less than 4.3% at 10 µs is predicted, which is more consistent with their experimental observations. Our findings are also consistent with the observations of Schaberle et al. who observed negligible triplets in 0.001 mM solutions in toluene or 0.39 mM solutions of chloroform, respectively. At these concentrations, the upper bound of the ISC rate constant, 3.08 × 10 6 s -1 , predicts triplet yields of 6.2% or less at 0.001 mM and 7.2% or less at 0.39 mM. Their data may show even less triplet formation than this (it is difficult to say without knowing the detection limit), but these values are consistent as upper bounds regardless.