Pair Correlations and Photoassociation Dynamics of Two Atoms in an Optical Tweezer

New techniques for individual atom preperation allow investigations of photoassociation using exactly two atoms, giving much better control over the process and the created molecule. We prepare exactly two Rb-85 atoms in the same internal state in an optical tweezer and photoassociate them.

We experimentally observe non-exponential decay of the atom pair which fundamentally differs from the dynamics in a many-atom ensemble, where photoassociation causes an exponential decay of the atomic population governed by a single rate coefficient that reaches a universal limit. This unique behavior is caused by the photoassociation process altering the atom-pair correlations as the process progresses. The observed rate coefficients for molecule formation from positively correlated atom pairs exceeds the unitarity limited rate coefficient found in many-atom ensembles. We compare the photoassociation dynamics of atom-pairs to those in a three-atom system, allowing us to probe the transition from two-atom to many-atom dynamics. Our results are underpinned by ab initio calculations.

Our findings show that this state-dependent photoassociation could be used as a new tool for the production or detection of atom-pair correlations in future experiments.