Ultracold molecules by photoassociation
Besides an interest in fundamental physics, ultracold molecules open prospects for various applications in the field of chemistry, metrology and quantum physics (eg. Quantum computing). The failure of techniques of laser cooling directly on the molecules, due to the complex structure of their energy levels, stimulated the search for alternative methods to produce them. In the lab we use one of these methods, defined photoassociation, which consists in the excitation by a suitable photon of two cold colliding atoms at an interatomic distance such as to form an excited dimer; this dimer in some cases may have a not negligibleprobability to decay into a molecule in the groundsingletstate or in the metastable triplet state. The molecules are then detected by the REMPItechnique(resonance enhanced multiphoton ionization), transforming them into molecular ions, selected by time-of-flightand detected by a MCP. After the first experiments onhomonuclearmolecules (Rb<sub>2</sub> and Cs<sub>2</sub>), in recent years we are studying RbCs molecules, thatin the ground stateare polar molecules, having a permanent electric dipole moment(1.22 Debye)in the presence of an electric field. Studies concern the best mechanisms for the formation and for the detection (including spectroscopic investigations) and the transfer offormedmolecules in well defined rovibrational states.