Measurement of Extinction Coefficients of Triplet Absorption and Quantum Yields of Triplet Formation*

A method for measuring ∊T, the molar extinction coefficient of triplet absorption, and ΦT, the quantum yield of triplet absorption, is described. The method which is applicable when the lifetime of the triplet state exceeds 0.1 sec, is comprised of two measurements. Values of ∊T are obtained from triplet absorbance measurements taken between 3100 and 7000Å; values of ∊TΦT are obtained from the rate of buildup of triplet absorbance in an excitation beam of known intensity. Results are given for 1,2 benzcoronene and 1,2 benzanthracene in EPA at −196°C and in polymethylmethacrylate at 23°C.