High-brightness, high-purity spin-polarized cesium beam

We describe a cesium atomic beam (${10}^{14}$ atoms ${\mathrm{s}}^{\mathrm{-}1}$, 6×${10}^{16}$ atoms ${\mathrm{sr}}^{\mathrm{-}1}$ ${\mathrm{s}}^{\mathrm{-}1}$) spin polarized using light from two diode lasers. Of the atoms, 95% may be placed into either the 6${\mathit{S}}_{1/2}$(F,${\mathit{m}}_{\mathit{F}}$)=(3,3) or (4,4) state, with less than 2×${10}^{\mathrm{-}4}$ of the atoms left in the depleted hyperfine level. The latter fraction rises linearly with atomic beam intensity because of reabsorption of light scattered during the optical pumping process. This and other effects limiting complete hyperfine pumping are discussed.