Photoassociative spectroscopy and formation of cold molecules

In the molecular photoassociation process, two free cold atoms absorb one p hoton by a resonant way, to create an excited molecule in a well defined re -vibrational state. The photoassociative spectroscopy of alkaline dimers yi elds accurate determinations for the long-range parts of molecular potentia l curves correlated to the first s + p asymptote. In contrast to atoms, las er cooling of molecules is very difficult because of the lack of a closed t wo-level scheme for recycling the population. The molecular photoassociatio n of cold atoms opens also a promising alternative for the formation of col d ground state molecules. Photoassociation of cold cesium atoms has permitt ed the first observation of translationally cold ground state molecules. Th e case of the cesium atom is very favorable because the 0(g)(-) and 1(u) pu rely long-range states below the dissociation limit 6s(1/2) + 6p(3/2) prese nt Condon points at intermediate distances. Such configurations offer rathe r efficient channels for the creation of singlet or triplet ground state Cs -2 molecules after spontaneous decay.