Atom-Dimer Scattering in a Three-Component Fermi Gas

Ultracold gases of three distinguishable particles with large scattering lengths are expected to show rich few-body physics related to the Efimov effect. We have created three different mixtures of ultracold Li-6 atoms and weakly bound Li-6(2) dimers consisting of atoms in three different hyperfine states and studied their inelastic decay via atom-dimer collisions. We have found resonant enhancement of the decay due to the crossing of Efimov-like trimer states with the atom-dimer continuum in one mixture as well as minima of the decay in another mixture, which we interpret as a suppression of exchange reactions of the type vertical bar 12 > + vertical bar 3 > -> vertical bar 23 > + vertical bar 1 >. Such a suppression is caused by interference between different decay paths and demonstrates the possibility of using Efimov physics to control the rate constants for molecular exchange reactions in the ultracold regime.