O(3P) + H2(v, j)-->OH + H:OH reactions

However, the existence of a high activation barrier in the reaction with ground state oxygen atoms limits its efficiency in cold gas. In this study we calculate the dependence of the reaction rate coefficient on the rotational and vibrational state of H_2_ and evaluate the impact on the abundance of OH in interstellar regions strongly irradiated by far-UV photons, where H_2_ can be efficiently pumped to excited vibrational states.

We use a recently calculated potential energy surface and carry out time-independent quantum mechanical scattering calculations to compute rate coefficients for the reaction O(^3^P)+H_2_(v,j)-->OH+H, with H_2_ in vibrational states v=0-7 and rotational states j=0-10. We find that the reaction becomes significantly faster with increasing vibrational quantum number of H_2_, although even for high vibrational states of H_2_ (v=4-5) for which the reaction is barrierless, the rate coefficient does not strictly attain the collision limit and still maintains a positive dependence with temperature.