Measurements of rate constants of O₂(b) quenching by CH₄, NO, N₂O at temperatures 300-800 K

Abstract

Electronically excited oxygen has an important place in the kinetic schemes of the processes taking place in the atmosphere, in the active medium of an oxygen-iodine laser, and in plasma-assisted combustion 1 . Over the past decades, a large amount of data on the rate constants of quenching O2(b) on a large number of collision partners has been accumulated. However, they mostly refer to the results of measurements at room temperature. In this paper, rate constants for the quenching of O2(b) by collisions with N2O, NO, and CH4 have been determined in the temperature range from 297 to 800 K, by the laserinduced fluorescence method. O2(b) was excited by pulses from a tunable dye laser, and the deactivation kinetics were followed via observing the temporal behavior of the b 1 Σg + → X 3 Σgfluorescence. From the analysis of experimental results, the following temperature dependencies of the quenching rate constants by these gases were obtained, and could be represented by the expressions: kNO=(1.77±0.2)×10 -24 ×T 3.5 exp(1138±37/T); kN2O=(2.63±0.14)×10 -16 ×T 1.5 ×exp(590±26/T) and kCH4=(3.54±0.4)×10 -18 ×T 1.5 ×exp(-220±24/T) cm 3 s -1 . All of the rate constants measured at room temperature were found to be in good agreement with previously reported values.