Imaging of the charge-transfer reaction of spin-orbit state-selected Ar + ( 2 P 3/2 ) with N 2 reveals vibrational-state-specific mechanisms.

Charge-transfer reactions are ubiquitous and play important roles in various gaseous environments, but, despite a long history of extensive research, our understanding of their dynamics at the quantum state-to-state level is still lacking. Here we report quantum-state-resolved experiments for the paradigmatic charge-transfer reaction Ar +  + N 2  → Ar + N 2 + using a three-dimensional velocity-map imaging crossed-beam apparatus with the Ar + beam prepared exclusively in the spin-orbit state 2 P 3/2 . High-resolution scattering images show strong dependence of rotational and angular distributions on the vibrational quantum number of the N 2 + product. Trajectory surface-hopping calculations, which semi-quantitatively reproduce the experimental observations, support the existence of two distinct charge-transfer mechanisms. One of these, in the dominant N 2 + (v' = 1) channel, is the well-known long-distance harpooning mechanism. However, the highly rotationally excited products in the forward direction are attributed to a hard-collision glory scattering mechanism, which occurs on account of the strong attraction between the collisional partners counterbalanced by the short-range repulsive interaction.