NMR studies of angular momentum transfer and nuclear spin relaxation.

摘要

Spin-exchange optical pumping is a process by which photons are used to polarize alkali-vapor atoms, which subsequently transfer their angular momentum to noble-gas nuclei through spin exchange. The high nuclear polarization this produces in the noble gas can be detected by nuclear magnetic resonance (NMR). This dissertation presents an investigation of these spin-exchange interactions as well as a study of the relaxation of noble-gas nuclei to their equilibrium polarization.; We begin with a description of NMR and the experimental techniques used throughout this work. Next we address the issue of nuclear relaxation in solid 129Xe, showing conclusively that the vacancy-mediated dipole-dipole interaction is the dominant relaxation mechanism at temperatures above 120 K. We further demonstrate that NMR of alkali metals can be used to detect trace impurities in alkali-vapor cells, data which indicate that these cells can acquire impurities through intrinsic alkali-glass interactions. Finally we present the first evidence of spin-exchange optical pumping of a solid, reporting experiments in which 133Cs nuclei were successfully polarized in excess of the thermal equilibrium limit. These results open up new possibilities in the field of artificially-polarized materials.