Valiev and co-workers found that for most molecules a value of 1.6 × 10 14 s -1 for S 1 → S 0 transitions is appropriate. The results calculated using Equation (Table ) infer rate constants are within a reasonable degrees of error with respect to experimental values, for almost all case study chromophores. Free-base porphyrin was shown to show strong disagreement when compared to experiment. Since the first singlet excited state of this chromophore is shown to be optically dark , calculations within the Franck-Condon regime are not adequate. A similar disagreement is observed for some of the polyacenes, since the S 1 states in many of the smaller variants are not pure, but mixed states . Earlier work by Baryshnikov and co-workers agreed with the results on the circulene poor internal conversion rate constants. Valiev & Kurten applied this model to photocatalysis models to probe hydrogen shifts of peroxyl radicals, and found internal conversion to dominate the reaction cross-section.