The outcomes following collisional quenching of electronically excited OH A 2Σ+ by O2 and CO are examined in a combined experimental and theoretical study. The atomic products from reactive quenching are probed using two-photon laser-induced fluorescence to obtain H-atom Doppler profiles, O (3PJ) atom fine structure distributions, and the relative yields of these products with H2, O2, and CO collision partners. The corresponding H-atom translational energy distributions are extracted for the H + O3 and H + CO2 product channels, in the latter case revealing that most of the available energy is funneled into internal excitation of CO2. The experimental product branching ratios show that the O-atom producing pathways are the dominant outcomes of quenching: the OH A 2Σ+ + O2 → O + HO2 channel accounts for 48(3)% of products and the OH A 2Σ+ + CO → O + HCO channel yields 76(5)% of products. In addition, quenching of OH A 2Σ+ by O2 generates H + O3 products [12(3)%] and returns OH to its ground X 2Π electronic state [40(1)%; L. P. Dempsey, T. D. Sechler, C. Murray, and M. I. Lester, J. Phys. Chem. A113, 6851 (2009) https://doi.org/10.1021/jp902935c]. Quenching of OH A 2Σ+ by CO also yields H + CO2 reaction products [26(5)%]; however, OH X 2Π (v = 0,1) products from nonreactive quenching are not observed. Theoretical studies characterize the properties of energy minimized conical intersections in four regions of strong nonadiabatic coupling accessible from the OH A 2Σ+ + CO asymptote. Three of these regions have the O-side of OH pointing toward CO, which lead to atomic H and vibrationally excited CO2 products and/or nonreactive quenching. In the fourth region, energy minimized points are located on a seam of conical intersection from the OH A 2Σ+ + CO asymptote to an energy minimized crossing with an extended OH bond length and the H-side of OH pointing toward CO in a bent configuration. This region, exoergic with respect to the reaction asymptote, is likely to be the origin of the dominant O + HCO product channel.

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