A scheme for reactive electronic quenching of OH(A2Σ+) through collisions with H2 is proposed, supported by electronic structure data obtained from multireference configuration interaction wave functions. The scheme represents an insertion pathway that leads from the initial 32A state in the reactant channel, into a valence region, where a nonadiabatic transition to the 22A state, enabled by a 22A–32A conical intersection seam occurs. Once on the 22A state, insertion of HO into H2 provides access to a linking region and, after surmounting a small barrier, to a region where the low-lying electronic states are Rydberg in character, corresponding to the 3s, 3px, 3py, and 3pz states of OH3+. In the Rydberg region, a deep well on the 22A potential energy surface exists. Direct passage from the 22A state to ground state products, H2O(X1A1) + H, is precluded by an energy barrier so that an intermediate complex can be formed on the 22A potential energy surface. As the insertion is facilitated by rehybridization of the oxygen orbitals from sp to sp3 in the linking region, nonplanar approach of HO to H2 is favored. The precipitous change in electronic structure from valence to Rydberg character renders the linking region inaccessible on the 32A potential energy surface. From the 22A state in the Rydberg region, access to the H2O + H product channel is enabled by repeated passage through a region of appreciable 12A–22A derivative coupling or by radiative decay. This scheme supplements other pathways in which nonadiabatic transitions from the 22A state to the 12A state in the valence region enable both planar and nonplanar insertion and abstraction paths leading directly to H2O products.

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