Quantum capture, adiabatic channel, and classical trajectory study of the high pressure rate constant of the reaction H+O2-->HO2 between 0 and 5000 K.

Limiting high pressure rate constants for the recombination reaction H+O(2)-->HO(2) are modeled between 0 and 5000 K on an ab initio potential. Quantum capture theory is employed for the temperature range from 0 to about 1 K, while classical trajectory calculations are suitable for covering temperatures above about 200 K. The intermediate temperature range is analyzed by adiabatic channel capture theory. The system is characterized by transition-state switching from outer transition states in the long-range-C(6)R(6) potential to inner transition states in the range of a "shoulder" of the potential. The limiting high pressure rate constants from the trajectory calculations are sufficient for comparison with the experimental data which are available over the range from 300 to 900 K. Specific rate constants k(E,J) for HO(2) dissociation are also given and analyzed with respect to internal consistency with capture cross sections.