EFFICIENCY OF THE PHOTOPROCESSES LEADING TO SINGLET OXYGEN (1δg) GENERATION BY α‐TERTHIENYL: OPTICAL ABSORPTION, OPTOACOUSTIC CALORIMETRY AND INFRARED LUMINESCENCE STUDIES*

Abstract
The triplet energy of .alpha.-terthienyl has been determined by heavy atom-induced optical absorption; the value of 39.7 .+-. 1.5 kcal/mol is consistent with earlier energy transfer work. Combining this result with calorimetric data from optoacoustic calorimetry indicates that intersystem crossing occurs with at least 90% efficiency in polar and non-polar solvents. The quantum yields for singlet oxygen formation via energy transfer from triplet .alpha.-terthienyl have been obtained from time-resolved measurements of its IR phosphorescence; these yields are in the 0.6-0.8 range in non-polar and polar (hydroxylic and non-hydroxylic) solvents.
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