Studies of Polarized Atomic Hydrogen

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Polarized atomic hydrogen (H*) is in a gaseous phase even at zero K due to the large quantum effects and is expected to show Bose condensation if atomic hydrogen with a sufficient density is cooled at low temperatures. Studies of the quantum nature of the atomic hydrogen gas at very low temperatures have attracted much attention. In this research project, we studied the following: (1) We studied the 2-dimensional (2-D) H* adsorbed on liquid helium surface and investigated the possibility to obtain the 2-D superfluidity, so called Kosteritz-Thuoless Transition. In this experiment atomic hydrogens were produced by a cryogenic discharge and were introduced into the buffer volume located in a high magnetic field and were polarized there. Some of the stored H* was introduced through a capillary into a sample cell. In the sample cell we prepared a small cold spot where H* were adsorbed and cooled. In order to reduce the surface recombination the surface of the cell was coated with a superfluid He film. We were able to cool the 2-D H* with a surface density of 10^<12>/cm^2 down to 85 mK. We found the percentage of the recombination heat dumped to the 2-D system was much less than 1.4%. We investigated the thermal coupling mechanism between the 2-D H* and the liquid He. (2) We studied spin diffusion constant of atomic hydrogen in He gas. This problem offers a unique opportunity to investigate the gas kinetics at very low temperatures on a microscopic basis. By using the Carr-Purcell-Meiboom-Gill Method to observe spin echoes nearly at zero field resonance, we determined diffusion constant of H in He gas and deduced a diffusion cross section. We determined the details of interaction potential between H and He. (3) The nuclear spin of H is also polarized and called H**. We discussed the feasibility of applying H* for elementary particle physics.