  We report here on the production of an ultracold gas of tightly bound Rb2
molecules in the ro-vibrational triplet ground state, close to quantum
degeneracy. This is achieved by optically transferring weakly bound Rb2
molecules to the absolute lowest level of the ground triplet potential with a
transfer efficiency of about 90%. The transfer takes place in a 3D optical
lattice which traps a sizeable fraction of the tightly bound molecules with a
lifetime exceeding 200 ms.
