Ion velocity map imaging study of the charge transfers from N2+/N+ to H2O.

Considering important roles of ion-molecule collision in planetary atmospheres, here we investigate the charge transfer dynamics of N2+/N+ + H2O → N2/N + H2O+ in the collision energy range of 0.42-2.09 eV. In the collisions with N2+, the H2O+ yield is populated in the bending-motion vibrational states of the A 2A1 state and its production efficiency is enhanced monotonously with the decrease in collision energy. The H2O+ velocity images recorded with the three-dimensional ion velocity map imaging technique exhibit two categories of spatial distributions: at relatively high energies, the narrow and forward-scattered distribution corresponds to the resonant or prompt charge transfer in large-impact-parameter collisions; small-impact-parameter or intimate collisions are preferred at the lower energies, leading to the H2O+ distribution closer to the center of masses. The charge transfers from N+ exhibit similar dynamics; by contrast, an intermediate complex (N⋯H2O)+ is more likely to be experienced in the low-energy intimate collision.