Collision-induced rotational excitation in N$2 + ( 2 Σ g + , v = ) –Ar$⁠: Comparison of computations and experiment

The collisional dynamics of N$2 + ( 2 Σ g + )$ cations with Ar atoms is studied using quasi-classical simulations. N$2 +$–Ar is a proxy to study cooling of molecular ions and interesting in its own right for molecule-to-atom charge transfer reactions. An accurate potential energy surface (PES) is constructed from a reproducing kernel Hilbert space (RKHS) interpolation based on high-level ab initio data. The global PES including the asymptotics is fully treated within the realm of RKHS. From several ten thousand trajectories, the final state distribution of the rotational quantum number of N$2 +$ after collision with Ar is determined. Contrary to the interpretation of previous experiments which indicate that up to 98% of collisions are elastic and conserve the quantum state, the present simulations find a considerably larger number of inelastic collisions which supports more recent findings.