The ${}_{}{}^3{}_{}{}^{}P_2^{}{}_{}{}^{}$ metastable atoms of neon have been optically oriented. This represents the first case of the optical pumping of non-$S$ state atoms. The optical-pumping process is described, and depolarization cross sections for collisions with ground-state neon and ground-state helium atoms measured. The cross section for collisional depolarization with helium is 4.30 ± 0.22 × ${10}^{-17\mathrm{}}$ ${\mathrm{cm}}^2$, and with neon is 166 ± 8 × ${10}^{-17\mathrm{}}$ ${\mathrm{cm}}^2$ at 300°K. The metastable ${}_{}{}^3{}_{}{}^{}P_2^{}{}_{}{}^{}$ atoms of Ar and Xe have also been optically pumped. As the polarizability of the noble-gas buffer increases, the collisional depolarization cross section approaches the diffusion cross section.

• Received 23 December 1968

DOI:https://doi.org/10.1103/PhysRev.180.83