In situ observation of non-polar to strongly polar atom-ion collision dynamics

The onset of collision dynamics between an ion and a Rydberg atom is studied in a regime characterized by a multitude of collision channels. These channels arise from coupling between a non-polar Rydberg state and numerous highly polar Stark states. The interaction potentials formed by the polar Stark states show a substantial difference in spatial gradient compared to the non-polar state leading to a separation of collisional timescales, which is observed in situ. For collision energies in the range of $k_\textrm{B}\cdot\mu$K to $k_\textrm{B}\cdot$K, the dynamics exhibit a counter-intuitive dependence on temperature, resulting in faster collision dynamics for cold - initially "slow" - systems. Dipole selection rules enable us to prepare the collision pair on the non-polar potential in a highly controlled manner, which determines occupation of the collision channels. The experimental observations are supported by semi-classical simulations, which model the pair state evolution and provide evidence for tunable non-adiabatic dynamics.