We therefore give the ISC rate constant an upper bound of 3.08 × 10 6 s -1 , i.e., the characteristic time scale of ISC in TIPS-Pn must be longer than 325 ns. This corresponds to a ISC quantum yield of ≤5.6% at 0.05 mM. The 8 ns time window we use in this study is significantly shorter than this time constant, and we note that ISC could possibly be shown to be even slower with a longer time-window TA experiment. equal to the experimental data. Even with this noise, there is a slight observable trend with time in the modeled data corresponding to an increase in T 1 absorption at 504 nm relative to the GSB. The difference between the shape of the experimental and modeled spectra (Fig. )), shows a negative trend as a function of time that is centered at 504 nm. This result confirms that the amount of T 1 predicted here using the upper bound for the ISC rate constant that we have determined is an overestimate, and thus the true ISC rate constant is lower than this value.