Abstract
Abstract— The extinction coefficient εT, of triplet benzophenone in benzene has been directly determined by absolute measurements of absorbed energy and triplet absorbance, ΔD0T, under demonstrably linear conditions where incident excitation energy, E0, and ground state absorbance, A0, are both extrapolated to zero. The result, 7220 ± 320 M‐1 cm‐1 at 530 nm, validates and slightly corrects many measurements relative to benzophenone of triplet extinction coefficients made by the energy transfer technique, and of triplet yields obtained by the comparative method.As E0 and A0 both decrease, ΔD0T becomes proportional to their product. In this situation, the ratio R= (1/A0)(dΔD0T/dE0) = (εT ‐ εG)φT. Measurements of R, referred to benzophenone, give (εT ‐ εG)φT for any substance, without necessity for absolute energy calibration.Both absolute and relative laser flash measurements on zinc tetraphenyl porphyrin (εT ‐ εG at 470 nm = 7.3 × 104M‐1 cm‐1) give φT= 0.83 ± 0.04.
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