Abstract
Optical pumping of Rb or Cs subject to relaxation through the formation of relatively long‐lived alkali‐rare‐gas molecular complexes is shown to yield a unique distribution of population throughout the magnetic sublevels of the alkali ground state. Large overpopulations of the sublevels of the upper hyperfine state are obtained for a particular range of the ratio of pumping rate to relaxation rate. The technique may make feasible the construction of a Cs maser.