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Abstract

In this work, the dynamics of anion-neutral interactions are studied in a hybrid atom-ion trap. An octupole radio-frequency trap is used for trapping anions, and a dark spontaneous-force optical trap is employed to create ultracold rubidium (Rb) atoms. Spatial density distributions of the ion and atom clouds are determined via photodetachment tomography and saturation absorption imaging, respectively. A method to map the ions’ translational temperature onto their time of flight to the detector is presented. This technique is applied to determine the temperature of OH−anions as they undergo laser-induced forced evaporative cooling to temperatures below 4 K. The dynamics of associative electronic detachment reaction between closed-shell anions OH−and alkali atoms are investigated where for a ground-state Rb the influence of a dipole-bound state as a reaction intermediate is observed. The interaction dynamics of Rb with OH−(H2O) are also explored, where a smaller atom-to-ion mass ratio favors sympathetic cooling via elastic collisions. For atomic O−, the detachment processes involving ground-state Rb are found to be closed and efficient anion sympathetic cooling, via ultracold Rb, is observed. These results present hybrid systems as a platform to investigate anion-neutral collision dynamics, particularly interesting for astrochemistry, fundamental physics, and quantum chemistry.