Absorption and fluorescence of toluene vapor at elevated temperatures
Absorption and fluorescence of the S0 S1 (pi,pi*) transition in toluene were studied in the temp. range 300 K to 1130 K and 300 K to 930 K, resp. Expts. are conducted in a shock-tube and in a heated flow-cell. Fluorescence spectra were studied after excitation at 248 nm and 266 nm using a N diluent at a total pressure of 1 bar. Over the temp. range studied the fluorescence quantum yield decreases exponentially by three orders of magnitude for 266 nm excitation and double exponentially by three orders of magnitude for 248 nm excitation. The fluorescence spectrum shifts to the red with increasing temp. The vibrational structure of the absorption spectrum found at ambient conditions vanishes >600 K The absorption feature broadens and the max. shifts to the red. Taking advantage of the distinctive temp. dependence of the fluorescence, the authors suggest potential techniques using toluene as a sensitive tracer mol. for temp. imaging in both homogeneously and inhomogeneously mixed flow-fields.
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