QUANTUM-MECHANICAL CALCULATION OF THE RATE-CONSTANT FOR THE REACTION H-2-]OH+O(O)

Quantum rate calculations for the H+O-2-->HO+O combustion reaction, as well as for the reverse reaction, are reported. Using the DMBE IV pot ential energy surface, the cumulative reaction probability N-0(E) has been directly computed for total angular momentum J=0, by means of the Seideman, Manthe and Miller Lanczos-based absorbing boundary conditio n method [J. Chem. Phys. 96, 4412 (1992); 99, 3411 (1993)]. Special at tention has been paid to the definition of the molecular basis set, an d to the sensitivity of the results to the absorbing potentials used i n the asymptotic regions. The N-0(E) results show very good overall ag reement with the coupled channel calculations of Pack et al. [J. Chem. Phys. 102, 5998 (1995)], although the highly oscillatory behavior jus t above threshold renders such a comparison difficult in that energy r ange. The behavior of the J not equal 0 cumulative reaction probabilit y has been estimated from calculations using the J(z)-conserving appro ximation for J values in the range 10-70. This allowed us to define wh ich reference geometry should be used in the J-shifting approximation, in order to compute the cumulative reaction probability N-J(E) for an y J value. By imposing conservation of the total energy within this ap proximation, the rate constants are shown to display better agreement with the experimental results. (C) 1998 American Institute of Physics. [S0021-9606(98)02609-9].