Gas Phase Oxygen Quenching Studies of Ketone Tracers for Laser-Induced Fluorescence Applications in Nitrogen Bath Gas

In this paper we report the quantitative oxygen quenching effect on laser-induced fluorescence of acetone, methyl ethyl ketone, and 3-pentanone at low pressures (approximate to 700torr) with oxygen partial pressures up to 450torr. Nitrogen was used as a bath gas in which these molecular tracers were added in different quantities according to their vapor pressure at room temperature. These tracers were excited by using a frequency-quadrupled, Q-switched, Nd:YAG laser (266nm). Stern-Volmer plots were found to be linear for all the tracers, suggesting that quenching is collisional in nature. Stern-Volmer coefficients (k(sv)) and quenching rate constants (k(q)) were calculated from Stern-Volmer plots. The effects of oxygen on the laser-induced fluorescence of acetone, methyl ethyl ketone, and 3-pentanone were compared with each other. Further, the Smoluchowski theory was used to calculate the quenching parameters and compared with the experimental results.