C-60 TRIPLET LIFETIMES - VIBRATIONAL-ENERGY DEPENDENCE FROM 0 TO 80000 CM(-1)

The persistence of the lowest electronically excited state of C-60 has been studied in the vapor phase at temperatures near 1000 K. Population decay of this triplet state is found to be nonexponential, reflecting the thermal distribution of vibrational energies among the sample molecules. The kinetic data can be quantitatively modeled by assuming an exponential dependence of triplet-state lifetime on vibrational energy content. Extrapolation of these findings to lower vibrational energies accounts for previously reported C-60 triplet lifetimes measured in condensed phases at temperatures down to 1 K. This study therefore provides a unified description of the 1000-fold variation in C-60 triplet state lifetime over the 0-80000 cm(-1) range of vibrational energies corresponding to temperatures between 0 and 1000 K.