Evidence of Quantum Chaos in Feshbach Resonances of Ultracold ⁸⁷Rb+²³Na⁸⁷Rb

We report the observation of magnetically tunable Feshbach resonances between ultracold ⁸⁷Rb atoms and ground-state ²³Na⁸⁷Rb molecules. More than 50 resonances have been observed in each of two different collisional channels in the magnetic field range of about 500 Gauss. Analyzing the distributions of the resonances statistically and comparing them to models based on random matrix theory, we obtain the first evidence of chaotic scattering in the atom-molecule system.