Statistical theory for the reaction N + OH → NO + H: thermal low-temperature rate constants

The reaction N + OH → NO + H involves the intermediate formation of NOH adducts which in part rearrange to HNO conformers. A statistical treatment of the process is developed in which an initial adiabatic channel capture of the reactants is accompanied by partial primary redissociation of the N OH collision pairs. A criterion for the extent of this primary redissociation in competition to the formation of randomized, long-lived, complex of NOH is proposed. The NOH adducts then may decompose to NO + H, rearrange in a unimolecular process to HNO, or undergo secondary redissociation back to the reactants N + OH, while HNO may also decompose to NO + H. As the reactants N( 4 S) + OH( 2 Π) have open electronic shells, non-Born-Oppenheimer effects have to be considered. Their influence on thermal rate constants of the reaction at low temperatures is illustrated and compared with such effects in other reactions such as C( 3 P) + OH( 2 Π). A statistical treatment of the reaction N + OH → NO + H is developed to characterize the redissociation processes by a state-specific criterion.