Abstract

We have observed that a beam of cesium atoms can be totally optically pumped into a particular and well defined quantum state, under circumstances that have not been previously considered. The usual mechanisms of optical pumping operate on the basis of selective excitation and atomic relaxation induced by the interaction of linearly or circularly polarized light with dipole allowed atomic transitions. For such cases the strength of the opcital pumping depends on the detuning of the laser from resonance, but the direction of the pumping (i.e. which levels get optically pumped) is independent of detuning. In the mechanism we discuss, the laser is linearly polarized, and the optical pumping direction is determined by the sign of the detuning of the laser from exact resonance. In our experiments, when the laser is at exact resonance, only the usual optical pumping, whose direction is frequency independent, is obtained. However, for a slight detuning to either side of the resonance, total atomic alignment into one of the two extremum Zeeman sublevels can be achieved.

© 1992 IQEC