Long-lived complexes and the role of chaos in ultracold molecular collisions

Thermally averaged lifetimes for complexes formed during ultracold elastic collisions of K$_2$ with Rb, from numerically-exact quantum-scattering calculations, are shown to be in remarkable agreement with the predictions of simple density-of-states models. The validity of such models is of current interest as they suggest the cause of trap loss in ultracold gases of alkali-dimers is long-lived complexes. Long-lived complexes correspond to narrow scattering resonances which we examine for the statistical signatures of quantum chaos, finding that the positions and widths of the resonances are in good agreement with the Wigner-Dyson and Porter-Thomas distributions respectively.