Production and Diagnosis of a Highly Spin-Polarized Na Beam

We describe optically pumping a beam of sodium atoms to >96% m _S and >92% m _S , m _I state selection. (We have accurately measured the population of every m _S , m _I state in the optically pumped beam.) For the optical pumping both ground hyperfine states are pumped, using single-mode cw dye-laser radiation tuned to the 3 S _1/2 –3 P _1/2 transition that is phase modulated in a LiTaO ₃ crystal to produce first-order sidebands at approximately the 1772-MHz hyperfine splitting of the ground state. The z -directed optical pumping is performed in a z -directed magnetic field of ~5 G. The state-selected atoms then move, in ~1 cm, into an ~200 G, z -directed field. The downstream probe laser beam is scanned through the 3 S _1/2 ( m _S , m _I ) → 3 P _3/2 ( m _S ′, m _I ) transitions, which are spectroscopically resolved at 200 G, and the fluorescence intensities portray the residual populations in each of the eight 3 S _1/2 states.