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Laser optical pumping of high-density Rb in polarized He 3 targets

1994; American Physical Society; Volume: 49; Issue: 5 Linguagem: Inglês

10.1103/physreva.49.3854

1538-4446

Mark E. Wagshul, T. E. Chupp,

Cold Atom Physics and Bose-Einstein Condensates

We have investigated high-density Rb optical pumping in polarized $^{3}\mathrm{He}$ targets and present measurements of collisional relaxation rates and studies of diffusion-driven wall relaxation of the Rb polarization. We show that a boundary layer resides in the vicinity of the cell walls within which a polarization gradient is established by diffusion. Absorption of the incident laser radiation within this layer leads to a striking decrease in optical-pumping efficiency for resonant light but has little effect for off-resonant light. Our theory introduces polarization-dependent slowing of optical pumping rates due to the Rb nuclear spin. We have observed a strong frequency dependence of the optical-pumping efficiency, consistent with our theoretical predictions. We report the following rate constants for collisional relaxation of Rb polarization: due to Rb (${\mathit{k}}_{\mathrm{Rb}\mathrm{\ensuremath{-}}\mathrm{Rb}}$=8\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}13}$ ${\mathrm{cm}}^{3}$/s), due to ${\mathrm{N}}_{2}$ (${\mathit{k}}_{\mathrm{N}2\mathrm{\ensuremath{-}}}$Rb=8\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}18}$ ${\mathrm{cm}}^{3}$/s), and due to $^{3}\mathrm{He}$, an upper limit of (${\mathit{k}}^{3}$He-Rb\ensuremath{\le}2\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}18}$ ${\mathrm{cm}}^{3}$/s). The data and model presented are used to predict laser power and intensity requirements for high-density polarized $^{3}\mathrm{He}$ targets.