Time-dependent quantum mechanical calculations on H+O2 for total angular momentum J>0.: III.: Total cross sections

The H+O-2--> OH+O reaction has been studied with a time-dependent wave packet method for total angular momentum J=15, 20, 25, 35. This work is a continuation of previous studies for J less than or equal to 10. The calculations were performed combining a real wave packet method with the Coriolis coupled method on parallel computers. We find that for most energies there is a monotonic decrease of reaction probability with increasing J. Nevertheless, due to the 2J+1 degeneracy, higher angular momentum states contribute significantly to the total reaction cross section. A smoothing/interpolation/extrapolation scheme is employed to compute total reaction cross sections. These cross sections are compared with quasiclassical results on the same potential energy surface, and the most recent experimental cross sections. Comparisons with quasiclassical results show the significance of zero-point energy constraints. The quantum mechanical theoretical cross sections are smaller than the experimental ones everywhere, suggesting that a more accurate potential energy surface is required. There is also some possibility that nonadiabatic effects play a role in this reaction. (C) 2000 American Institute of Physics. [S0021-9606(00)01248-4].