Reaction of the Month: December 1995

Reaction of the Month

December 1995

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This month we feature the room temperature pressure falloff curve for the crucially important reaction OH + NO2 -> HONO2. This reaction is the subject of a paper we recently submitted to the Journal of Geophysical Research. Click here for a postscript version. Here is the caption (OK, so it's long. What else is new?):

Full analysis of the pressure falloff for the reaction OH + NO2 -> products at 300 K, showing rate constant vs. nitrogen number density. The studies indicated in the righthand panel are identified by symbol shape. The different bath gases identified in the lefthand panel determine symbol color, with the exception of our own work (in nitrogen), which is plotted in black for emphasis. Symbols appear in the righhand panel for each carrier gas use in each study. Collisional efficiencies derived from our fit, relative to nitrogen, are shown with the bath gases in the lefthand panel. Number densities (the ordinate) for gases other than nitrogen are scaled by these efficiencies for the plot. The high and low pressure limiting rate constants are plotted as intersecting black lines, while the model results and 95% confidence intervals are plotted as solid and dashed black curves. The model results plotted here are $k_0 = {\left(3.39 \pm 0.26 \right) \times 10^{-30}}$, $k_\infty = \left(4.77 \pm 1.04 \right) \times 10^{-11}$, and ${.30 \pm .03}$, for the full Troe reduced falloff parameterization. The ratios of the data to the model results are shown in the bottom panel. Note in particular that the two current recommendations lie between 20 and 30% above our model results over the entire range of pressures pertinent to atmospheric chemistry.


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Last updated: 13Aug97 by nmd