Precision test of statistical dynamics with state-to-state ultracold chemistry

Chemical reactions between quantum-state-controlled molecules at ultralow temperatures provide an ideal platform for testing state-of-the-art quantum chemistry and scattering calculations. In this talk, I will discuss our recent measurements of the complete product quantum state distribution for the exchange reaction 2KRb → K₂ + Rb₂, where the ultracold KRb reactants are prepared in their rovibronic ground state. By combining state-selective photoionization with ion velocity-map imaging, we perform state-resolved coincident detection of the reaction products. In this way, we measure the scattering probabilities for all 57 rotational state-pairs that are allowed by the reaction exoergicity. Our results exhibit reasonable agreement with a state-counting model based on statistical theory, but also reveal several state-pairs which show significant deviations. Specifically, we observe a highly suppressed scattering probability for the state-pair closest to the exoergicity limit, a result of the long-range potential inhibiting the escape of products.