Temperature and deuteration effects on the fluorescence of benzenoid solutions

Deuterium isotope substitution and temperature effects on the fluorescence of toluene and p-xylene solutions have been investigated. Values of fluorescence quantum yields were measured between −80° to 70°C for p-xylene, p-xylened10, toluene and toluene-d8 and also fluorescence decay times at room temperature. The influence of several experimental factors on the fluorescence intensity at various temperatures was investigated and corrections were applied to obtain correct quantum yields. The results are compatible with an absence of a normal deuteration effect, and are independent of temperature, for both molecules, and show the existence of a non-radiative transition from the first excited single state to the ground state.