Theoretical determination of rate constants for vibrational relaxation and reaction of OH(X 2Π, v=1) with O(3P) atoms

Collisions of the vibrationally excited OH(v=1) molecule with atomic oxygen are investigated theoretically using a coupled-states, statistical capture (CS-ST) model. Vibrational relaxation can occur by inelastic scattering, and the vibrationally excited molecule can also be removed by reaction to form O-2 in both the ground (X (3)Sigma(-)(g)) and first excited (a (1)Delta(g)) state. In the former case, reaction occurs on the lowest potential energy surface of (2)A'' symmetry, and, in the latter case, by reaction on the lowest potential energy surface of (2)A' symmetry. We report new ab initio potential energy surfaces for both these states in the product and reactant regions necessary for application of the coupled-states, statistical method. Comparison with exact, reactive scattering calculations within the J-shifting approximation indicate that the CS-ST rate constants for removal of OH(v=1) can be expected to be reasonably accurate. Our calculated rate constants at 300 K agree well with the experimental results of Khachatrian and Dagdigian [Chem. Phys. Lett. 415, 1 (2005)]. Reaction to yield O-2 (X (3)Sigma(-)(g)) is the dominant removal pathway. At subthermal temperatures, the rate constants for the various vibrational quenching processes all increase down to T congruent to 60 K and then decrease at lower temperature. (C) 2008 American Institute of Physics.