Photoassociation of molecules out of an ultracold gas was thefirst successful approach to create a gas of molecules in the electronic ground state at translational temperatures in the micro-Kelvin range. 1 The major challenge in synthesizing a molecule from a pair of free atoms consists in overcoming the large gap between the initial interatomic pair distance in an ultracold gas (typically in the micrometer range) and the final binding length of a diatomic molecule in the ground state (typically in the subnanometer range). As shown in Figure 1a, photoassociation thus proceeds via a weakly bound excited molecular state, which can be excited at long interatomic distances, and subsequent stabilization of the molecule by spontaneous emission at shorter range. In this way, photoassociation explores the interatomic