Acetone Photophysics at Near Critical to Supercritical Conditions

Abstract

The photophysics of vapor and liquid acetone are experimentally examined from subcritical to supercritical conditions with 266 nm excitation, motivated by an interest in using acetone to study transcritical fuel injection and mixing. The fluorescence quantum yield for acetone vapor is measured, and the values are compared to the models of Thurber and Braeuer. The measured fluorescence yields are found to be similar to the model predictions. In addition, the two models are found to converge as the excitation wavelength or pressure increases. For 266 nm excitation, the difference between the model predictions is approximately 2% for pressures above 30 atm. Liquid acetone fluorescence and phosphorescence data are obtained at various pressures and temperatures. The liquid fluorescence signals do not change with pressure and temperature. In addition, liquid fluorescence is not affected by oxygen quenching, as compared to vapor fluorescence. It was found that the oxygen saturation concentration in liquid acetone is extremely small compared to the concentration needed to affect the fluorescence signal. The liquid phosphorescence is also found to be invariant with pressure, but it decreases exponentially as the temperature of the liquid is raised. A corresponding decrease in the measured phosphorescence lifetimes indicates that the phosphorescence yield is reduced asymptotically with temperature, with little change above ~375 K. This is likely due to acetone-acetone quenching of the excited triplet state. Most of the liquid acetone photophysics can be explained as a high density limit of the vapor photophysics models.

Experimental Investigation of Liquid Fragmentation In Hypersonic Crossflow

“…An example of seeding approach is Planar Laser Induced Exciplex Fluorescence (PLIEF) technique [77]. Planar Laser Induced Fluorescence and Phosphorescence (PLIFP) is a novel spectroscopic technique, first proposed and validated by [145,146] for an acetone transcritical jet. The technique is capable of characterising quantitatively the mixing behaviour of fluids in a transcritical/supercritical environment as well as identifying the location of the subcritical/supercritical interface.…”