Analysis of laser-induced-fluorescence carbon monoxide measurements in turbulent nonpremixed flames.

The influence of fluctuating concentrations and temperature on the laser-induced-fluorescence (LIF) measurement of CO in turbulent flames is described, under conditions in which the fluorescence and the temperature are measured independently. The analysis shows that correlations between CO concentration and temperature can bias the averaged mole fraction extracted from LIF measurements. The magnitude of the bias can exceed the order of the average CO mole fraction.

Avoidance of the photochemical production of oxygen atoms in one-dimensional, two-photon laser-induced fluorescence imaging.

We demonstrate that one-dimensional, two-photon laser-induced fluorescence imaging of oxygen atoms in flames can be achieved with reasonable signal intensities and spatial resolution but without the interference caused by the photolysis of O(2), by the use of a beam telescope instead of a focusing lens. The increase in probed volume (and concomitantly the number of excitable atoms) caused by the larger beam diameter in the telescope experiments offsets, to a certain extent, the loss in signal that is due to the reduced laser fluence. Further, the results show that the "correct" dependence of the fluorescence intensity on laser fluence (in this case quadratic) does not guarantee the absence of photochemistry.