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 combustion1. 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 CH4have been determined in the temperature range from 297 to 800 K, by the laser-induced 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 b1Σg+→ X3Σg-fluorescence. 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×T3.5exp(1138±37/T); kN2O=(2.63±0.14)×10-16×T1.5×exp(590±26/T) and kCH4=(3.54±0.4)×10-18×T1.5×exp(-220±24/T) cm3s-1. All of the rate constants measured at room temperature were found to be in good agreement with previously reported values.
Highlights
Gas phase processes with oxygen molecules in second electronically excited state b1 has been studied extensively in last decades, due to the importance of these processes in the terrestrial atmosphere [1,2,3], oxygen-containing gas discharges [4,5,6] and combustion [7,8,9,10]
Studies of the O2(b1 ) deactivation at room temperature by molecules relevant to combustion are represented by many works: CH4 [12,13,14,15,16,17], NO [18], N2O [12,13,18,19,20]
An oxygen-quencher gas mixture flowed through the fluorescence cell (FC), which consisted of a cylindrical quartz tube 40 cm long, with an internal diameter of 15 mm, the ends were sealed by quartz windows, mounted at an angle
Summary
Gas phase processes with oxygen molecules in second electronically excited state b1 has been studied extensively in last decades, due to the importance of these processes in the terrestrial atmosphere [1,2,3], oxygen-containing gas discharges [4,5,6] and combustion [7,8,9,10]. The measurements were made by observing the decay profiles of emission intensity from excited oxygen O2(b1 ) on the addition to the oxygen flow of the quencher, using the excitation of b1 state by pulsed dye laser. An oxygen-quencher gas mixture flowed through the fluorescence cell (FC), which consisted of a cylindrical quartz tube 40 cm long, with an internal diameter of 15 mm, the ends were sealed by quartz windows, mounted at an angle. To observe emission from O2(b1 ) a rectangular window, 2 cm long and 1 cm high was located in the center of FC. This aperture was free of insulating materials and heating tape. The gas temperature in the LIF region was measured by a thermocouple
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