3-Pentanone LIF at elevated temperatures and pressures: measurements and modeling

The objective of this study is to investigate 3-pentanone fluorescence experiments in a constant volume vessel at high temperature and high pressure to underline the influent parameters in conditions close to those encountered in internal combustion engines. To obtain quantitative analysis, measured fluorescence signals must be corrected by considering the influence of preponderant parameters such as temperature, pressure and gas composition. Quantitative dependences of fluorescence on thermodynamic parameters are measured and compared with the predictions of a photophysical model, which combines the effects of temperature, pressure, excitation wavelength on fluorescence quantum yield. The increase of 3-pentanone fluorescence with pressure is due to the vibrational relaxation of energy levels. The fluorescence decreases with increasing temperature, except at low temperature where the fluorescence increase is due to an activation of intersystem crossing between triplet toward singlet levels. The influences of thermodynamic parameters are based on an increase of the non-radiative decay rate with the vibrational energy level of excited electronic state and the important collisions to remove the excess vibrational energy. Experimental and calculated results show a satisfactory agreement.