Quantum scattering in a juggling atomic fountain

We vertically launch two balls of laser-cooled atoms from a magneto-optical trap to demonstrate a juggling atomic fountain. By varying the delay between the launch of the two balls of atoms from 7 ms to 20 ms, we can arrange collisions between them at the top of the trajectory with energies from 19 to 150 muK At these energies, the scattering is non-classical and only the lowest angular momentum quantum states (partial waves) contribute. We measure the velocity distribution of the scattered atoms to distinguish different partial waves by their differential cross section. Since each partial wave contributes to the total differential cross section as a quantum amplitude, the velocity distribution is very sensitive to small contributions of higher partial waves, due to the interference between them.;In this work we prepare and scatter 6 S1/2F = 4 m = 4 atoms with 6 S1/2F = 3 m = 3 atoms. In this way, we demonstrate a complete scattering experiment---state-to-state velocity-selected differential crossed-beam scattering at muK energies. We see the velocity distribution change from pure s-wave to pure p-wave scattering as we increase the energy, and there is evidence for d-wave scattering at the highest energies. The partial wave energy dependence suggests a negative (triplet) s-wave scattering length, and we infer a p-wave scattering length of (-107(6) a0) 3 and a d-wave scattering length of (-52(7)a0) 5.;Finally, we will present suggestions for future investigation, such as measuring collisions in other hyperfine magnetic substates. In addition, we present a novel method of directly measuring the scattering phase shifts with an atomic clock type experiment.