Energy Scaling of Cold Atom-Atom-Ion Three-Body Recombination

We study three-body recombination of Ba+ + Rh + Rh in the mK regime where a single Ba-138(+) ion in a Paul trap is immersed into a cloud of ultracold Rb-87 atoms. We measure the energy dependence of the three-body rate coefficient k3 and compare the results to the theoretical prediction, k(3) proportional to E-col-(3/4), where Eco1 is the collision energy. We find agreement if we assume that the nonthermal ion energy distribution is determined by at least two different micromotion induced energy scales. Furthermore, using classical trajectory calculations we predict how the median binding energy of the formed molecules scales with the collision energy. Our studies give new insights into the kinetics of an ion immersed in an ultracold atom cloud and yield important prospects for atom-ion experiments targeting the s-wave regime.