Optical Pumping of Helium in theS13Metastable State

Abstract

The alignment of ${\mathrm{He}}^4$ atoms in the ($n=2\mathrm{}$, metastable) ${}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$ state is described. Metastable atoms are produced by an rf discharge in a glass tube containing a few mm of pure helium, and the one micron pumping light ($2{}_{}{}^3{}_{}{}^{}P-2\mathrm{}{}_{}{}^3{}_{}{}^{}S$) is provided by a helium lamp. A resonance signal is obtained from radio frequency disorientation by monitoring the transmitted pumping light. The double maximum line shape of this signal for strong rf magnetic fields is discussed. Included also is a discussion of the angular dependence of the signal when unpolarized light is used and an explanation of the inversion of the resonance signal for certain densities of the metastable helium atoms.