Dynamics of the O H2O charge-transfer reaction and its implications for space-borne measurements

O⁺(⁴S) + H₂O charge-transfer cross-section and product-ion time-of-flight measurements are presented over a center-of-mass collision energy range of 0.2–15 eV. The results are obtained with a newly constructed guided-ion beam experiment. The measured energy dependence of the charge-transfer crosssection agrees well with previous measurements and ADO model predictions of Bates Chem. Phys. Lett. 82, 396 (1981) Proc. R. Soc. Lond. A384, 289 (1982) Chem. Phys. Lett. 111, 428 (1984)] at low collision energies, but exhibits significant differences at collision energies above 2 eV. The product kinetic energy analysis shows that most of the product ions are produced with near-thermal kinetic energies. At low collision energies, a significant backscattered channel is observed that is associated with complex formation. This channel exhibits a cross-section of approximately 1.4 Ųat a collision energy of 2.65 eV, corresponding to a laboratory ion energy of 5 eV.