OH production from the reaction of vibrationally excited H₂ 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 H₂, which is formed via collisional energy transfer from O₂ (b ¹∑⁺ _g). Using published rate coefficients and altitude profiles for the chemical 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 water with excited state oxygen atoms, O(¹D). The fraction of total OH produced from the proposed mechanism is estimated to reach 16% at 100 km.