Optical Pumping inHe3

Abstract

Nuclear polarization of ${\mathrm{He}}^3$ has been performed using optical pumping techniques. The polarization is produced in the triplet metastable levels and transferred to the ground-state atoms by metastability exchange processes. The cross section for this process has been measured by two different methods, giving the results $\sigma =(6.1\mathrm{}\pm 1)\times {10}^{-16\mathrm{}}$ ${\mathrm{cm}}^2$ and $\sigma =(7.9\mathrm{}\pm 2)\times {10}^{-16\mathrm{}}$ ${\mathrm{cm}}^2$. One of the methods involved a spectroscopic determination of the density of metastable atoms in a weak discharge in ${\mathrm{He}}^3$, which was found to vary between 12.5 and 3.5×${10}^{10}$/cc. It was shown that one hyperfine component only ($F=\frac{1}{2}\to \frac{3}{2}$) of the $2{}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}-2\mathrm{}{}_{}{}^3{}_{}{}^{}P_0^{}{}_{}{}^{}$ line of ${\mathrm{He}}^3$ is excited by light from a ${\mathrm{He}}^4$ lamp. For this reason a previously quoted relation between the degree of polarization and the optical pumping signal needs to be modified.