Quantum statistical study of the C+ + OH -> CO + H+/CO+ + H reaction: Reaction rate and product branching ratio at interstellar temperatures

摘要

The C+ + OH reaction is an important process in the interstellar synthesis of the CO molecule and the CO+ ion. This reaction has two possible chemical outcomes, namely, formation of CO + H+ and CO+ + H products. Formation of CO + H+ occurs on the ground 1(1)A ' potential energy surface (PES), while CO+ + H can be formed on the 1(3)A ' and 2(1)A ' PESs. The stationary points on these three PESs have been found in explicitly correlated internally contracted multireference configuration interaction (icMRCI-F12a+Q) calculations. The entrance channel on the 1(1)A ' PES is barrierless, and the barriers on the 1(3)A ' and 2(1)A ' PESs are submerged so that the reaction to form both sets of products can occur at interstellar temperatures. The quantum statistical method of Manolopoulos and co-workers was employed with the three PESs in the reactant channel to compute the total reaction cross section and rate coefficient, as well as the product branching ratio, as a function of temperature. These PESs can be adiabatically accessed by the ground spin-orbit state, C+(P-2(1/2)), and the rate coefficient for the reaction of this state was estimated by invoking the adiabatic approximation.