Measurements of Acetone Fluorescence and Phosphorescence at High Pressures and Temperatures
Laser-induced fluorescence and phosphorescence signals of liquid acetone at pressures from 1 to 15 atm were measured and analyzed. Liquid acetone, which was preprocessed to minimize any dissolved oxygen, was injected as a low velocity jet into a pressurized chamber with either an air or nitrogen co-flow. The actone was excited at 266 nm. The laser-induced fluorescence intensity from the liquid was found to be invariant with pressure and co-flow conditions. The measured phosphorescence lifetimes were also found to independent of pressure, for both nitrogen and air environments. The phosphorescence lifetime for the liquid was measured to be ~1 μs, which is significantly smaller than the lifetime for acetone vapor (200 μs). This is likely due to self-quenching by acetone. The effect is further seen in the phosphorescence to fluorescence (P/F) ratio comparison between the liquid and vapor. The P/F ratio for liquid is 0.012, which is much smaller than the vapor value of 9.0. The overall phosphorescence intensities, however, were seen to decrease in the air co-flow cases compared to the nitrogen co-flow. Diffusion of oxygen into the liquid jet was observed, and the estimated concentration was found to be a few orders of magnitude less than the saturated concentration.
Simultaneous imaging of temperature and mole fraction using acetone planar laser-induced fluorescence
Abstract Imaging of concentration with acetone PLIF has become popular in mixing investigations. More recently, studies of the temperature dependences of acetone fluorescence have enabled quantitative imaging of temperature using single- or dual-wavelength excitation strategies. We present here the first demonstration of simultaneous imaging of temperature and mole fraction with acetone PLIF. Laser excitation is at 248 and 308 nm; the resulting fluorescence images are captured by an interline transfer CCD camera capable of acquiring two frames with a separation in time of as little as 500 ns. In addition to adding temperature imaging capability, this dual-wavelength approach enables mole fraction to be accurately measured in non-isothermal flows. Tests in a heated turbulent jet demonstrate the ability to record instantaneous mole fraction and temperature structure. The expected correspondence of the temperature and concentration fields is observed, and mean values of these quantities derived from image averaging show the expected radial and centerline profiles as the jet becomes fully developed.
Fragment Rotational State Distributions From The Dissociation Of NeIBr: Experimental And Theoretical Results
The IBr fragment rotational state distributions that result when the NeIBr van der Waals molecule undergoes vibrational predissociation have been measured in a pump–probe laser‐induced fluorescence experiment. Independent of initial vibrational state and the number of quanta of vibrational energy lost from the I–Br coordinate, the rotational distributions extend over the full range of energetically accessible states. From the observation of energetic constraints on the rotational distribution, the dissociation energy (D0) is calculated to be 65.5±1.2 cm−1 for the A electronic state, v=16. For the X electronic state, v=0, D0=71.8±1.2 cm−1. Quantum mechanical bound state calculations carried out on a model A electronic state potential energy surface are in quantitative agreement with this result. The rotational distributions are broader than that predicted by either a Franck–Condon or classical impulsive model for the dissociation. The distributions are qualitatively in accord with classical trajectory calc...