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Title: Rate constants, 1100{le}T{le}2000 K, for H + NO{sub 2} {r_arrow} OH + NO using two shock tube techniques : comparison of theory to experiment.

Rate constants for the reaction H + NO{sub 2} {yields} OH + NO have been measured over the temperature range 1100-2000 K in reflected shock wave experiments using two different methods of analysis. In both methods, the source of H-atoms is from ethyl radical decomposition in which the radicals are formed essentially instantaneously from the thermal decomposition of C{sub 2}H{sub 5}I. The first method uses atomic resonance absorption spectrometry (ARAS) to follow the temporal behavior of H-atoms. Experiments were performed under such low [C{sub 2}H{sub 5}I]{sub 0} that the title reaction could be chemically isolated, and the decay of H-atoms was strictly first-order. The results from these experiments can be summarized as k = (1.4 {+-} 0.3) x 10{sup -10} cm{sup 3} molecule{sup -1} s{sup -1} for 1100 {<=} T {<=} 1650 K. The second method utilizes a multipass optical system for observing the product radical, OH. A resonance lamp was used as the absorption source. Because this is the first OH-radical kinetics investigation from this laboratory, extensive calibration was required. This procedure resulted in a modified Beer's law description of the curve-of-growth, which could subsequently be used to convert absorption data to OH-radical profiles. Rate constants by this methodmore » required chemical simulation, and the final result can be summarized as k = (1.8 {+-} 0.2) x 10{sup -10} cm{sup 3} molecule{sup -1} s{sup -1} for 1250 {<=} T {<=} 2000 K. Because the results from the two methods statistically overlap, they can be combined giving k = (1.64 {+-} 0.30) x 10{sup -10} cm{sup 3} molecule{sup -1} s{sup -1} for 1100 {<=} T {<=} 2000 K. The present results are compared to earlier work at lower temperatures, and the combined database yields the temperature dependence over the large range, 195-2000 K. The combined results can be summarized as k = (1.47 {+-} 0.26) x 10{sup -10} cm3 molecule{sup -1} s{sup -1} for 195 {<=} T {<=} 2000 K. The reaction is subsequently considered theoretically using ab initio electronic structure calculations combined with modern dynamical theory to rationalize the thermal rate behavior.« less
Authors:
; ; ; ; ; ;
Publication Date:
OSTI Identifier:
949470
Report Number(s):
ANL/CHM/JA-41285
Journal ID: ISSN 1089-5639; JPCAFH; TRN: US201012%%264
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: J. Phys. Chem. A; Journal Volume: 106; Journal Issue: 36 ; Sep. 12, 2002
Research Org:
Argonne National Laboratory (ANL)
Sponsoring Org:
SC
Country of Publication:
United States
Language:
ENGLISH
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION; ELECTRONIC STRUCTURE; ETHYL RADICALS; OPTICAL SYSTEMS; RESONANCE ABSORPTION; SHOCK TUBES; SHOCK WAVES; TEMPERATURE DEPENDENCE