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

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 cm²/sec, respectively. The disorientation cross sections for sodium colliding with helium and neon are (3±{}4)×{}10^-26 and (1.8±{}0.6)×{}10^-24 cm², 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 cm² 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.