Three-body collisions in ultracold hybrid ion-atom systems

Hybrid ion-atom ultracold gases are particularly interesting in the context of three-body recombination and other collisional processes involving molecular ions. Absent in neutral ultracold matter, long-range interactions ion-atom systems give the prospect for a qualitatively new and interesting induction-dominated dynamics. At ultracold temperatures, three-body recombination becomes the dominant inelastic process generating atomic losses in ion-atom samples. We apply quantum scattering theory to model the inelastic collisions in this regime, where classical descriptions fail to properly describe the outcomes of experiments. We focus on describing the three-body processes in a sample comprised of trapped barium [1] or ytterbium [2] ions immersed in the ultracold lithium gas, where recently Feshbach resonances between an ion and neutral atoms were observed. We calculate the recombination rates into both neutral and ionic diatomic molecules across a series of ion-atom scattering lengths. We observe a novel type of interference phenomena possibly indicating a unique feature of recombination in ion-atom-atom systems. In order to characterize such interference phenomena, we study the nonadiabatic couplings driving the transitions along the relevant pathways. Additionally, we identify the appearance of weakly bound ionic triatomic molecules and predict their lifetimes.