Comparison of the cross-sections and thermal rate constants for the reactions of C(3PJ) atoms with O2 and NO

被引:54
作者
Geppert, WD [1 ]
Reignier, D
Stoecklin, T
Naulin, C
Costes, M
Chastaing, D
Le Picard, SD
Sims, IR
Smith, IWM
机构
[1] Univ Bordeaux 1, Lab Physicochim Mol, CNRS, UMR 5803, F-33405 Talence, France
[2] Univ Birmingham, Sch Chem, Birmingham B15 2TT, W Midlands, England
关键词
D O I
10.1039/b002583f
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
We report the results of two sets of experiments on each of the reactions C(P-3(J)) + O-2 --> CO + O (1) and C(P-3(J)) + NO --> CN + O (2a) --> CO + N (2b) In low temperature (15-295 K) kinetic experiments performed in a CRESU (Cinetique de Reaction en Ecoulement Supersonique Uniforme) apparatus, the rate constants for these two reactions were found to fit the following expressions: k(1) = (4.9 +/- 0.8) x 10(-11)(T.298 K) (-(0.32 +/- 0.08)) cm(3) molecule(-1) s(-1) and k(2) = (1.5 +/- 0.4) x 10(-10)(T/298 K)(-(0.16 +/- 0.14)) cm(3) molecule(-1) s(-1) In crossed beam experiments, relative cross-sections for products of the two reactions [CO from (1) and CN from (2a)] in specific vibrational levels were measured at collision energies (epsilon(tr)) between ca. 4 and 100 meV. The cross-sections are proportional to (epsilon(tr))(-0.94) for reaction (1) and to (epsilon(tr))(-0.72) for reaction (2a). Both sets of results demonstrate that these reactions proceed over potential energy surfaces with no barrier on the path from reactants to products. If the reaction cross-sections are independent of the rotational energy level of the reagents and of the distribution of C(P-3(J)) atoms over spin-orbit states, and if they exhibit the same dependence on relative translational energy below 4 meV as above, integration of the excitation functions leads to the rate constants exhibiting temperature dependences of k(1)(T) proportional to T-0.44 and k(2a)(T) proportional to T-0.22, in reasonable agreement with the direct measurements of the rate constants for reactions (1) and (2). The two sets of experimental results are also compared with theoretical calculations, based on the adiabatic capture centrifugal sudden approximation (ACCSA) model. The calculations correctly predict the temperature dependence of the rate constants for both reactions. The consistency of these three data sets is discussed.
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页码:2873 / 2881
页数:9
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