Résumé
Quantum rate calculations for the H+O2→HO+OH+O2→HO+O combustion reaction, as well as for the reverse reaction, are reported. Using the DMBE IV potential energy surface, the cumulative reaction probability N0(E)N0(E) has been directly computed for total angular momentum J=0, by means of the Seideman, Manthe and Miller Lanczos-based absorbing boundary condition method [J. Chem. Phys. 96, 4412 (1992); 99, 3411 (1993)]. Special attention has been paid to the definition of the molecular basis set, and to the sensitivity of the results to the absorbing potentials used in the asymptotic regions. The N0(E) results show very good overall agreement with the coupled channel calculations of Pack et al. [J. Chem. Phys. 102, 5998 (1995)], although the highly oscillatory behavior just above threshold renders such a comparison difficult in that energy range. The behavior of the J≠0 cumulative reaction probability has been estimated from calculations using the Jz-conserving approximation for J values in the range 10–70. This allowed us to define which reference geometry should be used in the J-shifting approximation, in order to compute the cumulative reaction probability NJ(E) for any J value. By imposing conservation of the total energy within this approximation, the rate constants are shown to display better agreement with the experimental results.