Quantum rainbow scattering at tunable velocities

Abstract

Elastic scattering cross sections are measured for lithium atoms colliding with rare-gas atoms and SF${}_{6}$ molecules at tunable relative velocities down to $\ensuremath{\sim}$50 m/s. Our scattering apparatus combines a velocity-tunable molecular beam with a magneto-optic trap which provides an ultracold cloud of lithium atoms as a scattering target. Comparison with theory reveals the quantum nature of the collision dynamics in the studied regime, including rainbows as well as orbiting resonances.