Selective Depopulation of the 6^2S_12 (F=3) Level in Cesium*

Optical pumping of cesium in a room-temperature vapor cell has been accomplished by means of a pulsed gallium arsenide laser. As the time-dependent laser frequency coincides with atomic transitions originating from the cesium ground-state hyperfine levels, light will be absorbed and thence re-emitted from the 6P state. The hyperfine splitting between the F = 3 and F = 4 ground-state levels can easily be resolved with this method. The lowest hyperfine level has been selectively depopulated. On this basis, the use of one or more GaAs lasers as a pumping source for cesium masers is indicated and discussed.