Articles written in Journal of Chemical Sciences
Volume 130 Issue 5 May 2018 Article ID 0054
The kinetic parameters of an important atmospheric reaction, CH3O2+NO2+M→CH3O2NO2+M, have been recorded by monitoring directly the changes in concentrations of methylperoxy radicals (CH3O2) in the gas phase employing a new mid-infrared quantum cascade laser (QCL)-based apparatus. CH3O2 radicals in our apparatus have been generated by pulsed UV laser (266 nm) photolysis of CH3I in a gaseous mixture with oxygen. The absorption band corresponding to the mid-infrared O-O stretching fundamental of the peroxy radical, within a narrow spectral range, 1070–1120 cm-1, has been recorded by tuning the wavelength of the QCL operated in CW mode. The kinetics of the aforementioned reaction of CH3O2 with NO2 has been followed by analyzing the changes of the infrared (QCL) decay profile of CH3O2 at 9.1 μm (1098.9 cm-1) maintaining a pseudo first order reaction condition. We noticed that the rate constant of the reaction at 298 K varies in the range of (1.21–3.08) ×10-12 cm3 molecule-1s-1 for changing the total pressure in the range of 75–730 mbar. The absorption cross-section of CH3O2 at the probe wavelength (1098.9 cm-1), has been estimated for the first time to be 8.3±0.4×10-20 cm2.
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