Line-shape changes due to optical pumping of Na in buffer gas

Abstract

We have observed a collapse of the Na hyperfine doublet into a single peak due to laser-induced optical pumping when the product of laser power and buffer gas pressure exceeds ∼0.1 mW Torr. The complex line shapes observed under these conditions have been quantitatively explained by a model which describes the laser-induced change in the population of the ground-state hyperfine levels and also includes pressure broadening and diffusion of atoms out of the laser beam. The line-shape distortion can occur at laser intensities ${10}^3$ below that required for radiative saturation, and must be considered in experiments involving the line shape or the population of the hyperfine levels.