Ion Velocity Map Imaging Study of the Reactive Collisions between Carbon Dioxide and Helium Ion.

The reactive collision between He + and CO 2 plays an important role in substance evolutions of the planetary CO 2 -rich atmosphere. Using a three-dimensional ion velocity map imaging technique, we investigate the low-energy ion-molecule reactions He + + CO 2 → He + CO 2 + /He + CO + + O/He + CO + O + . The velocity images of the products CO + and O + of dissociative charge-exchange reactions are distinctly different from those of charge-exchange product CO 2 + . The remarkable features of stereodynamics are observed in the dissociative charge-exchange reaction and are attributed to the spatial alignment of the initially random target CO 2 during the He + approach. Branching ratios of different channels of dissociative charge exchange are further obtained with the Doppler kinematics model, indicating a high preference for the energy-resonant channel.