Rate constant for the reaction atomic hydrogen + nitrogen dioxide from 195 to 400 K with FP-RF and DF-RF techniques

Abstract

Publication costs assisted by NASA Absolute rate constants for the reaction of atomic hydrogen with nitrogen dioxide have been measured over the temperature range 195-400 K with two independent techniques both of which utilize resonance fluorescence detection of H. The reaction was studied from 230 to 400 K with the flash photolysis-resonance fluorescence (FP-RF) technique. No variation with temperature was observed, the best representation for the rate constant being (1.32 ± 0.12) X 10-10 cm3 molecule-1 s-1. The discharge flow-resonance fluorescence (DF-RF) technique was also used to study the reaction over the temperature range 195-368 K. The results are best represented by the temperature-independent value of (1.50 ± 0.26) X 10-10 cm3 molecule-1 s-1. The mean value of the two determinations for 195 < 7 < 400 K is then kx = (1.41 ± 0.26) X 10-10 cm3 molecule-1 s-1 where the error is two standard deviations. The combined result is compared with previous results, both direct and indirect. The reaction is also considered theoretically, especially with regard to the question of the temperature dependence and the absolute magnitude of the rate constant.

Rate coefficients for the reactions of chlorine atoms with methanol and acetaldehyde

“…Literature data for k 1 and k 2 are given in Table III, together with the latest evaluations of the NASA and IUPAC panels and our current recommendation. In arriving at a recommendation for k 1 we reduced the weighting of the original absolute study by Michael et al [14], which lies considerably above the mean of the other values, and that of Wallington et al [17] which is not thought to be as reliable as the present study. Several of the studies [16,20] were not explicitly designed to measure k 1 and these studies have been given weights of 0.5 in the analysis, as has the study by Lightfoot et al [18] [17,21 -24].…”

“…The current study shows that the value of k 2 should be increased by about 5%, while the uncertainty can now be considered to be 15 -20%. Neither k 1 nor k 2 is expected to depend on temperature [14,18,23]. A general observation from this work is that measurement of the rate coefficients for even the simplest oxygenated organics is not straightforward, and the reactions should be studied by more than one technique whenever possible.…”

Consecutive reactions of aromatic-OH adducts with NO, NO&lt;sub&gt;2&lt;/sub&gt; and O&lt;sub&gt;2&lt;/sub&gt;: benzene, naphthalene, toluene, m- and p-xylene, hexamethylbenzene, phenol, m-cresol and aniline

“…The model is supplemented by the H+NO 2 rate constant, 1.3×10 −10 cm 3 s −1 (Wagner and Welzbacher, 1976;Michael et al, 1979), plus an H-atom diffusion term, and the triexponential solution is used in the analysis. Note that in the case of NO 2 as scavenger, coefficient a contains a term proportional to [NO 2 ].…”

Rate constants for the gas-phase reactions of Cl atoms with a series of ethers

“…The only absolute measurements reported so far were those of Michael et al [12] and Park et al [13] for the reaction of Cl with CH 3 OCH 3 , using FP-RF and DF-MS, respectively. The other measurements were performed using the relative rate technique.…”

“…Except for DME, all reported data so far on the reactions of Cl with these ethers have been performed using the relative rate technique [7 -11]. The absolute studies for the reaction of Cl with DME were performed by Michael et al [12] and Park et al [13] using the flash photolysis -fluorescence resonance (FP-FR) and discharge flow-mass spectrometry (DF-MS) techniques, respectively. To our knowledge, no data exist on the reaction of Cl with CH 3 CH 2 OC(CH 3 ) 3 .…”