OH-H₂ entrance channel complexes

The entrance channel to the OH + H₂ → H₂O + H hydrogen abstraction reaction has been investigated from several different experimental approaches and complementary theoretical calculations. Weakly bound complexes between the hydroxyl radical and molecular hydrogen have been stabilized within a shallow well in the entrance channel and characterized via electronic spectroscopy on the OH A²Σ⁺ - X²Π transition. Laser-induced fluorescence and fluorescence depletion experiments have revealed the binding energy of H₂/D₂ with ground state OH X²Π radicals, the intermolecular energy levels supported by the OH A²Σ⁺ (v′ = 0,1) + H₂/D₂ potential, and the OH-H₂/D₂ excited state dissociation limit. The OH X²Π + H₂ potentials have also been examined through inelastic scattering measurements on Λ-doublet state-selected OH with normal or para-H₂. Finally, photodetachment of an electron from the H₃O^- anion enabled the neutral reaction to be probed in conformations sampled by the two isomeric forms of the anion.