Temperature-dependent kinetic measurements and quasi-classical trajectory studies for the OH{sup +} + H{sub 2}/D{sub 2} → H{sub 2}O{sup +}/HDO{sup +} + H/D reactions
We have measured the temperature-dependent kinetics for the reactions of OH{sup +} with H{sub 2} and D{sub 2} using a selected ion flow tube apparatus. Reaction occurs via atom abstraction to result in H{sub 2}O{sup +}/HDO{sup +} + H/D. Room temperature rate coefficients are in agreement with prior measurements and resulting temperature dependences are T{sup 0.11} for the hydrogen and T{sup 0.25} for the deuterated reactions. This work is prompted in part by recent theoretical work that mapped a full-dimensional global potential energy surface of H{sub 3}O{sup +} for the OH{sup +} + H{sub 2} → H + H{sub 2}O{sup +} reaction [A. Li and H. Guo, J. Phys. Chem. A 118, 11168 (2014)], and reported results of quasi-classical trajectory calculations, which are extended to a wider temperature range and initial rotational state specification here. Our experimental results are in excellent agreement with these calculations which accurately predict the isotope effect in addition to an enhancement of the reaction rate constant due to the molecular rotation of OH{sup +}. The title reaction is of high importance to astrophysical models, and the temperature dependence of the rate coefficients determined here should now allow for better understanding of this reaction at temperatures more relevant to the interstellar medium.