Kinetics of the CH{sub 3}O{sub 2} + NO reaction: Temperature dependence of the overall rate constant and an improved upper limit for the CH{sub 3}ONO{sub 2} branching channel
- Hope Coll., Holland, MI (United States). Dept. of Chemistry
The methylperoxy radical (CH{sub 3}O{sub 2}) is an important intermediate species formed in the oxidation of methane in the atmosphere. Ozone levels in the atmosphere are directly affected by CH{sub 3}O{sub 2} reactions, which themselves are dependent on the levels of the nitrogen oxides (NO{sub x}). Under high NO{sub x} conditions (generally, lower tropospheric urban conditions), CH{sub 2}O{sub 2} reactions lead to the production of ozone. The overall rate constant and an upper limit for the CH{sub 2}ONO{sub 2} product channel for the CH{sub 2}O{sub 2} + NO reaction have been measured using the turbulent flow technique with high-pressure chemical ionization mass spectrometry for the detection of reactants and products. At room temperature and 100 Torr pressure, the rate constant was determined to be (7.8 {sup {minus}} 2.2) {times} 10{sup {minus}12} cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}. The temperature dependence of the rate constant was investigated between 295 and 203 K at pressures of either 100 or 200 Torr, and the data was fit to the following Arrhenius expression: (9.2{sub {minus}3.9}{sup +6.0} {times} 10{sup {minus}13}) exp [(600 {+-} 140)/T] cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}. Although the room-temperature rate constant value agrees well with the current recommendation for atmospheric modeling, the values for the rate constant at the lowest temperatures accessed in this study are about 50% higher than the same recommendation. No CH{sub 3}-ONO{sub 2} product was detected from the CH{sub 3}O{sub 2} + NO reaction, but an improved upper limit of 0.03 for this branching channel was determined.
- OSTI ID:
- 355566
- Journal Information:
- Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Journal Name: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory Journal Issue: 22 Vol. 103; ISSN 1089-5639; ISSN JPCAFH
- Country of Publication:
- United States
- Language:
- English
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