ADIABATIC POPULATION TRANSFER IN A MULTILEVEL SYSTEM

We report an experimental observation of coherent population transfer in a multilevel system by adiabatic following through a trapped state. Raman transitions between ground-state sublevels are induced by two p artially overlapping sigma+/- polarized laser beams, tuned to the hype rfine transition F=4 --> F'=4 of the cesium D2 line. An efficiency of more than 50% is observed for the m(F)=+4 --> m(F)=-4 population trans fer. The influence of other excited hyperfine levels on the transfer e fficiency is pointed out. The feasibility of the technique with counte rpropagating laser beams is also demonstrated.