Laser-polarized noble gases: a powerful probe for biology, medicine, and subatomic physics Gordon D. Cates, Professor of Physics, University of Virginia

For over a decade, laser-polarized noble gases such as He-3 and Xe-129 have proven useful for a broad range of scientific inquiries ranging from the investigation of pulmonary disease to the determination of the spin-structure of the neutron. While early efforts were limited in part by expensive laser systems, continuing advancements in solid- state lasers have enabled huge gains. Equally important has been the introduction of hybrid mixtures of alkali metals that can increase the efficiency of spin exchange by an order of magnitude. Magnetic resonance imaging (MRI) using laser-polarized noble gases has long provided images of the gas space of the human lung of unprecedented resolution. More recent work includes the use of diffusion- sensitizing pulse sequences to study lung microstructure, tagging techniques that enable the visualization, in real-time MRI movies, of gas flow during breathing, and potentially, the exploitation of chemical shifts in MR resonance frequencies to probe microscopic processes such as membrane transport. In subatomic physics, polarized He-3 targets now have figures of merit more than two orders of magnitude greater than during early SLAC experiments, a fact that has contributed to an ever growing role in unraveling the structure of the neutron.