Nuclear Magnetic Resonance in Solid Hydrogen with Various Ortho Concentrations

概要

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Nuclear magnetic resonance in solid hydrogen with various ortho concentrations was studied at low temperatures down to 1.17°K. The results on normal hydrogen were in agreement with those of Reif and Purcell. The width of the center peak at 4.2°K was 5.4 gauss in normal hydrogen and decreased with falling ortho concentration. In crystals with the concentration higher than 63 per cent, two side peaks with the separation of 39.5 gauss appeared at temperatures characteristic of the concentration. The center peak in low concentration hydrogen showed a fine structure at low temperatures. The theoretical considerations of Reif and Purcell concerning the state of solid hydrogen were examined and extended to interpret the results. Their assumption of asymmetric crystalline potential which lifts the rotational degeneracy of the ortho molecule was capable of explaining most of the experimental results in ortho-para mixures. The appearance of side peaks was attributed to the onset of cooperative ordering of the axes of rotation of the ortho molecules. The fine structure in low concentration hydrogen was considered to be due to the different local surroundings of the ortho molecules. The well-known specific heat anomaly and the ortho-para conversion in the solid were discussed on the same basis. The magnetic resonance absorption in solid deuterium was also studied in connection with the present problem.
東北大学の論文