Population distribution of product states following three-body recombination in an ultracold atomic gas

Three-body recombination is a collision process where two atoms combine to form a molecule and a third atom carries away part of the released reaction energy. Here, we experimentally determine for the first time the population distribution of the molecular reaction products after a three-body recombination for non-resonant particle interactions. The key to our measurements is a sensitive detection scheme that combines the photoionization of the molecules with subsequent ion trapping. Using an ultracold Rb-87 gas at very low kinetic energy below h x 20 kHz, we find a broad population of final states with binding energies of up to h x 750 GHz. This is in contrast with previous experiments, performed in the resonant interaction regime, that found a dominant population of only the most weakly bound molecular state or the occurrence of Efimov resonances. This work may contribute to the development of an in-depth model that can qualitatively and quantitatively predict the reaction products of three-body recombination.