Effect of Spin-Exchange Collisions on the Optical Orientation of Atomic Sodium

Abstract

The effect of spin-exchange collisions on the state populations obtained in an optically pumped ${\mathrm{Na}}^{23}$ vapor is studied in the limit of low light intensity. These state populations and hence the intensity of the rf Zeeman transitions are found theoretically to depend strongly on the spin-exchange cross sections. The various Zeeman rf transitions are found experimentally to be very different in intensity and this is interpreted as being partially due to spin-exchange collisions. From the intensity of the rf transitions in a magnetic field large enough to separate the six Zeeman components and from the observed relaxation time a spin-exchange cross section for two sodium atoms of $\pi {S_0}^2=6\mathrm{}\times {10}^{-14\mathrm{}}$ ${\mathrm{cm}}^2$ is found.