LASER OPTICAL-PUMPING OF HIGH-DENSITY RB IN POLARIZED HE-3 TARGETS

We have investigated high-density Rb optical pumping in polarized He-3 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. Abso rption of the incident laser radiation within this layer leads to a st riking decrease in optical-pumping efficiency for resonant light but h as little effect for off-resonant light. Our theory introduces polariz ation-dependent slowing of optical pumping rates due to the Rb nuclear spin. We have observed a strong frequency dependence of the optical-p umping efficiency, consistent with our theoretical predictions. We rep ort the following rate constants for collisional relaxation of Rb pola rization: due to Rb (k(Rb-Rb) = 8 X 10(-13) cm3/s), due to N2 (k(N2-Rb ) = 8 X 10(-18) cm3/s), and due to He-3, an upper limit of (k(He-3-Rb) less-than-or-equal-to 2 X 10(-18) CM3/S) . The data and model present ed are used to predict laser power and intensity requirements for high -density polarized He-3 targets.