Quasiclassical integral cross sections for H+H2(0,j=0,2)→H2(1,j′=1,3,5)+H

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Abstract
This paper presents state‐to‐state integral cross sections for the exchange reaction H+H2(0,j=0,2)→H2(1,j’=1,3,5)+H calculated from quasiclassical trajectories (QCT) on the Liu–Siegbahn–Truhlar–Horowitz (LSTH) potential energy surface in the relative energy range 0.4 to 1.2 eV. These are compared to results of exact quantum calculations at relatively low total energy (∼1 eV) [J. Z. H. Zhang and W. H. Miller, Chem. Phys. Lett. 1 5 3, 465 (1988)] and to those of the recent experiments of Kliner et al. [J. Chem. Phys. 9 4, 1069 (1991)]. Cross sections were calculated directly from trajectories starting in the (0,0) and (0,2) states and indirectly, using microscopic reversibility, from trajectories starting in (1,j’). The resulting QCT cross sections are in reasonable agreement with the quantum calculations, the indirect QCT results being the more satisfactory near threshold. The QCT cross sections behave smoothly with energy and, as expected, do not exhibit mild undulating structure such as is seen in the quantum calculations for (0,0)→(1,1); this is a quantum effect. Also included are QCT cross sections at translational energies near 1.28 and 1.90 eV which are relevant to the prompt reaction used in the experiments of Kliner et al. and for which quantum results are unavailable. The quasiclassical result was found to be somewhat higher than the experimental product ratio (1,3)/(1,1).

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