Study of the Spin-Relaxation Times and the Effects of Spin-Exchange Collisions in an Optically Oriented Sodium Vapor

Abstract

The spin-relaxation time of an optically oriented sodium vapor diffusing in a helium or neon buffer gas has been measured and analyzed by the method of Franzen. The diffusion coefficients for sodium in helium and neon are 1.0±0.3 and 0.50±0.17 ${\mathrm{cm}}^2$/sec, respectively. The disorientation cross sections for sodium colliding with helium and neon are (3±4)×${10}^{-26\mathrm{}}$ and (1.8±0.6)×${10}^{-24\mathrm{}}$ ${\mathrm{cm}}^2$, respectively. The radio-frequency (rf) Zeeman transitions of the sodium atoms in the ground state have been examined. An analysis of the effects of spin-exchange collisions between sodium atoms on the intensities and line shapes of the various Zeeman transitions is presented. From these studies a spin exchange cross section of (1-3)×${10}^{-14\mathrm{}}$ ${\mathrm{cm}}^2$ is estimated for two sodium atoms colliding. The main source of error in this measurement is probably lack of knowledge of the sodium vapor pressure in the sodium-absorption cells.