The nuclei of gaseous
129Xe atoms are polarized by spin exchange with optically pumped Rb vapor. The Xe gas is subsequently frozen. The nuclear polraizations of up to 25% are largely unaffected by freezing. The spin-lattice relaxation time
T1 was measured as a function of temperature, magnetic field, and isotopic composition. At 77 K and 1800 G,
T1 is limited to about 3 h by a new relaxation mechanism. The potential for accumulating large samples with even higher polarizations makes laser-polarized Xe ice promising for a wide variety of new experiments.
Atomic hydrogen (H) has recently been created in a long-lived state referred to as spin-polarized atomic hydrogen (H↓). A moderate density gas (n≃1017 atoms/ cc) has been produced at temperatures T≃400 mK. H↓ is predicted to be the only atomic substance that remains gaseous to T = 0 K; current experiments are consistent with this picture. Since the H↓ atoms behave as composite bosons the gas is expected to have a Bose-Einstein condensation (BEC) and related superfluidity at a sufficiently high density or low temperature. H↓ is expected to display spectacular static and dynamic properties. Since the gas is polarized, the dominant electronic magnetization, M⃗e, is proportional to the atomic density. In an inhomogeneous magnetic field M⃗e will also be highly inhomogeneous. BEC will be spatially localized and the static M⃗e should be an identifying feature of this state. The low-lying excitation spectrum should not only feature electronic and nuclear spin-transitions, but should also have magnetic translational modes of the gas. The experimental technique for stabilization of H↓ as well as many of the predicted magnetic properties are discussed.