Ultra-cold gases of molecules with permanent electric dipole moments offer fascinating prospects for fundamental physics studies. When two dipoles are oriented along the same direction, their interaction is repulsive when the dipoles are positioned side-by-side and attractive when they are positioned on top of each other. As a consequence it has been predicted that the occurrence of Bose-Einstein condensation (BEC) in a trapped gas of bosonic molecules interacting dominantly via dipole-dipole forces will be strongly influenced by the trapping geometry, i.e. that it can be switched on and off with an external knob. Apart from being anisotropic, the dipolar interaction is also long-range. Cold dipolar gases of fermions are therefore predicted to be excellent candidates for attaining super-fluid pairing in a single component gas. Producing ultra-cold dipolar gases is a formidable experimental challenge.
During the last few years the new technique of Stark deceleration has been successfully applied to a variety of neutral polar molecules, many of which have subsequently been confined in traps or stored in a ring. However, to be able to access the realm of the new and rich physics described above, the phase-space density (i.e. the number of molecules per unit volume and per unit momentum space) of the trapped molecules still needs to be significantly increased.
The aim of this proposal is to experimentally study the use of an ultra-cold cloud of Rb atoms as a refrigerant to further cool trapped samples of polar molecule s. To achieve this goal, we propose to overlay a recently demonstrated AC trap of ND3 molecules (which will be loaded from a Stark decelerator) with a magnetic trap holding 87Rb atoms. The successful implementation of this proposal would thus close the gap between the cold and ultra-cold regimes. This technique has been recently refined in the demonstration of a BEC of potassium atoms, which were cooled sympathetically with evaporatively cooled rubidium.
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