| I describe experiments with Bose-Einstein condensates (BEC) of 85Rb near a Feshbach resonance. The Feshbach resonance affects the collisions between atoms, allowing us to change the self-interaction energy of the BEC by applying a magnetic field. We used the Feshbach resonance to study the startling details of the BEC collapse after we abruptly switched the self-interaction from repulsive to attractive. This change caused a supernova-like implosion/explosion cycle, leaving behind a small remnant BEC. We also applied short magnetic field pulses toward the resonance to investigate the possibility of collisional coupling between atoms and diatomic molecules. We later created an atomic and molecular BEC superposition state and probed this state's coherence by applying two rapid magnetic field pulses. Careful measurements of the atom-molecule oscillation frequency allowed us to dramatically improve our determination of the Feshbach resonance parameters. All of these experiments have stimulated new theoretical work and have improved our understanding of the physics of resonant BEC. |
