{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"cd03a103bd73f7ade77e9d351e835d94a188aa2bb123845bb59e26e98845c230","created":"2026-10-03T07:17:58Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"7f02a393dc1cde081f1868491ecf5009337d875220705dc56ead6e11802fd16c","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"chem.reaction-dynamics.oh-methanol-low-t","kind":"phenomenon","literature_status":"partially-resolved","n":"1","parents":[],"plain":"The reaction of hydroxyl radicals with methanol runs nearly a hundred times faster at 63 K than at 200 K, the opposite of the usual slowing on cooling. Quantum tunneling of a hydrogen atom has been proposed, but whether the speed-up survives at the very low gas densities of interstellar clouds is disputed.","posed_since":"2013","precise":"For OH + CH3OH in Laval-nozzle flows from about 20 to 200 K, explain the rise of $k(T)$ by about two orders of magnitude below 200 K and its pressure dependence from a calculation combining the hydrogen-bonded pre-reaction complex, deep tunneling through the H-abstraction barrier and collisional stabilization, and determine $k(T)$ in the zero-pressure limit. An answer is a master-equation plus tunneling calculation on an accurate potential that reproduces measured $k(T, P)$.","problem_ref":null,"references":"","settled_by":"Pressure-resolved low-temperature kinetics compared with master-equation calculations that include instanton or quantum-scattering tunneling rates.","status_note":"Tunneling through a weakly bound complex was proposed in 2013 (Shannon, Blitz, Goddard, Heard, Nature Chemistry, https://doi.org/10.1038/nchem.1692); the size of the enhancement at interstellar densities is disputed.","title":"Low-temperature rate enhancement of the OH plus methanol 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