OH production from the reaction of vibrationally excited H-2 in the mesosphere

We propose a novel mechanism for OH production in the mesosphere (50-100 km ): the reaction of ground state oxygen atoms with vibrationally excited Hz, which is formed via collisional energy transfer from O-2 (b (1)Sigma (+)(g )). Using published rate coefficients and altitude profiles for the chemica l species involved, the contribution of this new mechanism to the total OH production rate has been estimated as a function of altitude. At altitudes above 75 km, the proposed reactions are as important as the reaction of wat er with excited state oxygen atoms, O(D-1). The fraction of total OH produc ed from the proposed mechanism is estimated to reach 16% at 100 km.