Imaging the state-to-state charge-transfer dynamics between the spin-orbit excited Ar + ( 2 P 1/2 ) ion and N 2 .

Ar + +N 2  → Ar+N 2 + has served as a paradigm for charge-transfer dynamics studies during the last several decades. Despite significant experimental and theoretical efforts on this model system, state-resolved experimental investigations on the microscopic charge-transfer mechanism between the spin-orbit excited Ar + ( 2 P 1/2 ) ion and N 2 have been rare. Here, we measure the first quantum state-to-state differential cross sections for Ar + +N 2  → Ar+N 2 + with the Ar + ion prepared exclusively in the spin-orbit excited state 2 P 1/2 on a crossed-beam setup with three-dimensional velocity-map imaging. Trajectory surface-hopping calculations qualitatively reproduce the vibrationally dependent rotational and angular distributions of the N 2 + product. Both the scattering images and theoretical calculations show that the charge-transfer dynamics of the spin-orbit excited Ar + ( 2 P 1/2 ) ion differs significantly from that of the spin-orbit ground Ar + ( 2 P 3/2 ) when colliding with N 2 . Such state-to-state information makes quantitative understanding of this benchmark charge-transfer reaction within reach.