Temperature dependence of the rates of photophysical processes of fluorenone

Fluorescence lifetimes, fluorescence quantum yields, and triplet yields have been measured as a function of temperature in solvents of different polarity. The rate coefficients for the dominant photophysical processes depopulating the fluorescent have been found to depend on the solvent and temperature. The solvent dependence is attributed to the different extent energy shift for the various excited states involved in these processes. The experimental results require the assumption temperature-dependent and -independent singlet-triplet intersystem crossing rates. The temperature-dependent process identified as a thermoneutral or endothermic transition from the lowest excited singlet to a higher triplet state.