Absolute total cross sections for the ion–molecule reaction O+(4S o)+H2O

Absolute total cross sections for H2O+ and OH+ formed by the O+(4So)+H2O reaction have been measured in the center-of-mass collision energy (Ec.m.) range of ≊0.1–60 eV. The cross sections for H2O+ are greater than those reported previously. The structure observed in the cross section curve for OH+ suggests that the OH++OH channel is produced at Ec.m.≊0.1–5.0 eV via a long-lived complex mechanism, while the OH++O+H channel is formed at Ec.m.≊5–60 eV by a short range charge transfer-predissociation pathway.