Experiments and prospects for ultracold molecules

The molecular photoassociation of cold atoms is one of the alternatives for the formation of cold molecules. In a photoassociation process, two atoms absorb one photon to form a cold molecule in a ro-vibrational level of an electronically excited state. Unfortunately, for most of the considered configurations, excited molecules dissociate after spontaneous emission. Long-range states below the first excited dissociation limits 6s + 6p of the cesium dimer present configurations with Condon points at intermediate distances, offering efficient channels for the formation of ground state Cs₂ molecules after spontaneous decay. Temperatures of the molecular cloud as low as 20 μK and formation rates of 0.1 cold molecule per second and per atom are measured. The possibility to prepare cold molecules in a well defined ro-vibrational level of the ground state through stimulated Raman photoassociation is also demonstrated.