Elastic scattering cross sections are measured for lithium atoms colliding with rare-gas atoms and SF${}_6$ molecules at tunable relative velocities down to $\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.

• Received 28 June 2012

DOI:https://doi.org/10.1103/PhysRevA.86.062711