Polarization of HELIUM-3 by Spin Exchange with High-Density Laser Optically Pumped Rubidium Vapor

This thesis presents the theoretical and experimental investigations of laser optical pumping in an optically thick alkali-metal vapor used as a tool for polarization of high density samples of gaseous ^3He via spin exchange. In the limit of a dense vapor, the alkali polarization process becomes nonlinear and the theoretical and experimental analysis is greatly complicated. The theoretical background for understanding polarization processes in optically thick vapors and for calculating spatial polarization dependencies is presented. Experimental techniques are also developed and used to measure two specific aspects of the vapor polarization: spin destruction rates due to Rb-Rb, Rb-N_2 and Rb-^3 He collisions via transient measurements, and steady state effects due to wall induced spin relaxation. The results for the spin destruction measurements are: <sigma_{SD}upsilon > (Rb - Rb) = (8.11 +/- 0.33) times 10^{-13} cm^3 /s, <sigma_{SD }upsilon> (Rb - N_2) = (9.38 +/- 0.22) times 10^{ -18} cm^3/s and <sigma_{SD}upsilon > (Rb - ^3He) = (2.29 +/- 0.23) times 10^{-18} cm ^3/s. The steady state measurements show that in a glass vapor cell a significant decrease in alkali polarization can be experienced due to the resonant absorption of light within a thin boundary layer at the front wall, the thickness of which is given approximately in terms of the incident light intensity I(0) by l_ {D} ~ sqrt{10.8D/(I(0) sigma_0)}. Numerical methods are developed to model the alkali vapor polarization and used to illustrate the ultimate limitations of the spin exchange-optical pumping technique for producing dense and highly polarized ^3He gas samples.