Rotational state changes in collisions of diatomic molecular ions with atomic ions
Phys. Rev. A 113, 042816 – Published 16 April, 2026
DOI: https://doi.org/10.1103/y3zq-t7n8
Abstract
We investigate rotational state changes in a single collision of diatomic molecular ions, polar or apolar, with an atomic ion. Rotational state changes may occur since the angular degree of freedom of the molecular ions interacts with the electric field due to the atomic ion. Thanks to the very different time and energy scales of translational and rotational motion, we may treat the collision classically and describe only the rotations quantum mechanically. We first investigate a number of example systems numerically and then derive closed-form approximations for the rotational excitation per collision, depending on the scattering energy and the molecular parameters. These findings provide the basis for estimating the accumulated rotational excitation in sympathetic cooling of molecular ions by laser-cooled atomic ions [J. M. Berglund et al., Phys. Rev. A 113, 042817 (2026)] which involves many single collisions.
