A combination of high-level quantum-chemical simulations and sophisticated transition state theory analyses is employed in a study of the temperature dependence of the N_2H + OH -> HNNOH recombination reaction. The implications for the branching between N_2H + OH and N_2 + H_2O in the NH_2 + NO reaction are also explored. The transition state partition function for the N_2H + OH recombination reaction is evauated with a direct implementation of variable reaction coordinate (VRC) transition state theory (TST). The orientation dependent interaction energies are directly determined at the CAS + 1 + 2/cc-pvdz leve. Corrections for basis set limitations are obtained via calculations along the cis and trans minimum energy paths employing an approx aug-pvtz basis set. The calculated rate constant for the N_2H + OH -> HNNOH recombination is found to decrease significantly with increasing temperature, in aggreement with the predictions of our earlier theoretical study. Conventional transition state theory analyses, employing new coupled cluster estimates for the vibrational frequencies and energies at the saddlepoints along the NH_2 + NO reaction pathway, are coupled with the VRC-TST analyses for the N_2H + OH channels to provide estimates for the branching in the NH_2 + NO reaction. Modest variations in the exothermicity of the reaction (1-2 kcal mol~(-1)), and in a few of the saddlepoint energies (2-4 kcal mol~(-1)), yield TST based predictions for the branching fraction that are in satisfactory agreement with related experimental results. The unmodified results are in reasonable agreement for higher temperatures, but predict too low a branching ratio near room temperature, as well as too steep an initial rise.
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