Vibrational state resolved measurements of differential cross sections for H + +O2 charge transfer collisions

Vibrational state-to-state charge transfer cross sections have been obtained for H⁺+O₂ collisions at E_cm =23.0 eV in a differential scattering experiment by measuring the product H atom energy distribution in the range 0°≤θ≤11°. The results show a strong dependence of the distribution of vibrational transition probabilities P(O₂, v=0→O⁺₂, v″) on the scattering angle. At very low angles (θ≲2°) we find a strongly enhanced contribution of the more resonant states v″=3-6 compared to a Franck-Condon distribution, which is peaked at v″=1 and, on the other hand, at moderate angles of about θ=4° comes very close to the measured spectra. At even larger angles increasing deviations from the Franck-Condon distribution towards larger excitation of higher vibrational states are observed. An explanation of these and the related results for the nonexchange collisions leading to neutral O₂ vibrational excitation is given in terms of the underlying potential energy surfaces.