Radio-frequency coupling of a Bose-Einstein condensate in a TOP trap

A radio-frequency (RF) transition is used to convert a pure F = 2, m (F) = 2 Rb-87 Bose-Einstein condensate confined in a TOP trap into a mixture of F = 2, m (F) = 2 and F = 2, m (F) = 1 states. We show that the nature of thi s coupling process is strongly influenced by the presence of the time-varyi ng field of the TOP trap, and complicated by the presence of multiple Zeema n substates. In particular, the effective Rabi frequency associated with th e applied RF field is not constant across the spatial extent of the cloud l eading to a complex geometry for atom-laser output coupling and 'averaging out' of Rabi oscillations. Further, a time-varying detuning can give rise t o complex spatial structures.