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Introduction

This work is a continuation of our research [1,2] on the important combustion reaction:

$\displaystyle \rm H(^2S) + O_2 (^3\Sigma_g^-) \longrightarrow OH (^2\Pi) + O (^3P).$      

This reaction is a rate determining step in the combustion of hydrogen and hydrocarbons, and accounts for approximately 80 % of the O$_2$ consumption in a typical hydrocarbon-air flame at atmospheric pressure.[3] This reaction has been studied extensively both experimentally [4,5,6,7,8,9,10,11,12,13,14,15,16,17,18] and theoretically,[1,2,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44] because of its role in combustion chemistry. (Note that this list of references is not exhaustive. For more references, see e.g., Refs. th:anth1998,th:pack1993,in:mill1990,in:yang1995).

Dynamical studies of this reaction have mainly used three different potential energy surfaces (PES's), the Melius-Blint surface,[47] the DMBE IV surface of Pastrana et al,[48] and the Diatomics-in-Molecules (DIM) surface of Kendrick and Pack.[49] Until recently, only quasi-classical calculations were possible.[19,20,21,22,23,24,25,26,27,28,29] In the last five years, however, full quantum mechanical calculations been performed either for total angular momentum $J=0$[30,31,32,33,34,35,36,37,38,39,40] or using approximate methods to treat $J > 0$.[41,42,43,44]

In several recent articles, Refs. th:anth1998 and th:anth1999 we have published quantum mechanical studies for $J > 0$ in which total angular momentum, $J$, is treated rigorously. In Ref. th:anth1998, Paper I, we presented total reaction probabilities for $J=0,1,2$ and $5$. In Ref. th:anth1999, paper II, we presented total reaction probabilities for $J = 10$, and compared the rigorous Coriolis-coupled (CC) results with helicity-conserving (HC) results for $J= 1,2,5$ and $10$ using two different body-fixed axis systems. We demonstrated that inclusion of the Coriolis terms was very important for an accurate calculation of the reaction probability.

In this paper we extend our Coriolis-coupled calculations to even higher angular momentum: $J = 15, 20, 25$ and $35$. Our goal is to compute the total reaction cross section of the H($^2$S) + O$_2$ ( $^3\Sigma_{\rm g}^-$) reaction to compare with the most recent experimental results of Volpp and Wolfrum.[50] We also compare our results to classical trajectory calculations of the reaction cross section using the same potential energy surface (DMBE IV).[25] In a future publication,[51] we will compare these Coriolis coupled cross sections to those obtained with various approximate methods.

The organization of the paper is as follows. In Sec. II we present the theory and computational details used for the large $J$ calculations. In Sec. III we outline the details of the reaction cross section calculations. In Sec. IVA we present results for the reaction probabilities as a function of energy and total angular momentum. In Sec. IVB we present our reaction cross sections and compare with experiment and with classical trajectory calculations. Finally, in Sec. V we discuss our results and present our conclusions.


next up previous
Next: Theory and Computational details Up: Time-dependent quantum mechanical calculations Previous: Time-dependent quantum mechanical calculations
Anthony J. H. M. Meijer 2000-10-05