Experiments and prospects for ultracold molecules

The molecular photoassociation of cold atoms is one of the alternatives fur the formation of cold molecules. In a photoassociation process, two atoms absorb one photon to form a cold molecule in a re-vibrational level of an e lectronically excited state. Unfortunately, for most of the considered conf igurations, excited molecules dissociate after spontaneous emission. Long-r ange states below the first excited dissociation limits 6s + 6p of the cesi um dimer present configurations with Condon points at intermediate distance s, offering efficient channels for the formation of ground state Cs-2 molec ules after spontaneous decay. Temperatures of the molecular cloud as low as 20 muK and formation rates of 0.1 cold molecule per second and per atom ar e measured. The possibility to prepare cold molecules in a well defined re- vibrational level of the ground state through stimulated Raman photoassocia tion is also demonstrated.