Kinetics of OH(v= 0, 1) and OD(v= 0, 1) with CO and the mechanism of the OH + CO reaction

Abstract

Rate constants have been measured for the removal of OH(v= 0), OD(v= 0), OH(v= 1) and OD(v= 1) in collisions with CO. At room temperature (298 ± 4 K) and in 18 or 25 Torr argon, the values obtained were (k/10^–13 cm³ molecule^–1 s^–1)= 1.53 ± 0.15, 0.55 ± 0.1, 10 ± 2 and 9.5 ± 2, respectively. Our results for OH(v= 0) and OD(v= 0) agree well with those of other workers. The previously undetermined rate constants for OH(v= 1) and OD(v= 1) with CO are believed to correspond to those for formation of an (HOCO) adduct which can decompose either to H + CO₂ or back to OH + CO, but with vibrational relaxation of the OH. Based on this proposition, transition-state theory calculations have been performed on the elementary processes which occur when OH, OD and CO collide. The calculations successfully explain the values of the rate constants in these systems and their dependence on temperature, pressure, isotopic substitution and reagent excitation.