Coherent splitting of Bose-Einstein condensed atoms with optically inducedBragg diffraction

We have observed Bragg diffraction of a Bose-Einstein condensate of sodium atoms by a moving, periodic, optical potential. The coherent process of Bra gg diffraction produced a splitting of the condensate with unidirectional m omentum transfer. Using the momentum selectivity of the Bragg process, we s eparated a condensate component with a momentum width narrower than that of the original condensate. By repeatedly pulsing the optical potential while the atoms were trapped, we observed the trajectory of the split atomic wav e packets in the confining magnetic potential.