| Because of the burgeoning applications of laser-polarized 129 Xe in biomedicine, materials, and fundamental physics, the 129Xe relaxation mechanisms in gaseous and solid laser-polarized Xe have been extensively studied. We now extend those investigations to the liquid phase. By measuring the 129Xe relaxation rate in liquid Xe as a function of magnetic field, temperature, and container surface, we determine that the major relaxation mechanisms are interaction with the surface and spin-rotation between pairs of Xe atoms. In addition, we have developed an elegant technique where, by the use of a single radio frequency, we match the Rabi frequency of surface protons to the 129Xe Larmor frequency. The increase in 129Xe relaxation rate caused by such a resonant condition shows that the dipole-dipole coupling between surface protons and 129Xe has a significant contribution to the zero-field relaxation rate of 129Xe.; The 129Xe lifetime in the liquid is found to be on the order of 20–30 minutes and has only a mild dependence on temperature, magnetic field, and surface environment. Its insensitivity to these parameters makes it a convenient method for the transportation of large quantities of laser-polarized 129Xe (as needed, for example, for magnetic resonance imaging of the human lungs). Furthermore, we explore in this thesis another promising application of liquid Xe in which the large nuclear polarization of 129Xe (∼20%) has been transferred through cross-relaxation to other spins dissolved in the liquid Xe. We have measured enhanced NMR signals for 1H that are more than a factor of 45 larger than thermal polarization signals at 200 K and 14 kG. For 13C we have seen signal enhancements of over 70. Furthermore, in dissolving toluene in liquid Xe, we have observed different enhancements of the ring and methyl proton signals. The lifetimes of the enhancements are on the order of ∼20 min. |
