Molecular oxygen generation from the reaction of water cations with oxygen atoms

The oxywater cation (H₂OO⁺), previously shown to form barrierlessly in the gas phase from water cations and atomic oxygen, is proposed here potentially to possess a ²A″ ←⁴A″ excitation leading to the H₂⋯O₂ ⁺ complex. This complex could then easily decompose into molecular hydrogen and the molecular oxygen cation. The present quantum chemical study shows that the necessary electronic transition takes place in the range of 1.92 eV (645 nm), in the orange-red range of the visible and solar spectrum, and dissociation of the complex only requires 5.8 kcal/mol (0.25 eV). Such a process for the abiotic, gas phase formation of O₂ would only need to be photocatalyzed by visible wavelength photons. Hence, such a process could produce O₂ at the mesosphere/stratosphere boundary as climate change is driving more water into the upper atmosphere, in the comet 67P/Churyumov-Gerasimenko where surprisingly high levels of O₂ have been observed, or at gas-surface (ice) interfaces.