Max-Planck-Institute for Nuclear Physics under the supervision of

This thesis reports on experiments with dilute gases consisting of distinguishable fermions whose interaction can be tuned over a wide range. These experiments cover the creation of a molecular Bose-Einstein Condensate (mBEC) as well as the first experiments on a three component degenerate Fermi mixture. To create a mBEC we start with a magneto-optical trap (MOT) of 2×108 fermionic 6 Li atoms. At a temperature of 410µK a mixture of the two lowest hyperfine states of 6Li is transferred into an optical dipole trap and evaporatively cooled. These fermions are bound to bosonic molecules as soon as their temperature drops below their binding energy. Further cooling leads to condensation of these molecules into a mBEC of about 100000 particles at a temperature of approxi-mately 30 nK. Further experiments make use of the wide tunability of the interaction between the three lowest hyperfine states of 6 Li by means of Feshbach resonances. Em-ploying RF transitions between these states allows for creating a mixture of three distinguishable fermions. This was achieved for the first time in our experiment