Pressure Studies on the Nuclear Magnetic Resonance of Solid Hydrogen between 1.2° and 14°K

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Abstract
The nuclear magnetic resonance spectrum of solid hydrogen (75% ortho) has been studied as a function of temperature from 1.2°K to 14°K and of pressures from one to three hundred atmospheres. At 10°K the absorption signal broadens from less than one gauss to 5.3 gauss between slope extrema as the temperature is lowered and self-diffusion ceases. When pressure is applied, this broadening is shifted to higher temperatures by a sizable amount. With 230 atmospheres, a shift of 3.2°K was observed. Correlation times and activation energies of self-diffusion have been computed for each of the transitions at various pressures. The activation energies are linearly dependent upon the transition temperatures. The lower transition at 1.5°K in which some rotational degeneracy is removed was also investigated with various pressures. Pressures up to 216 atmospheres did not shift the transition temperature to any observable extent. Pressures up to 337 atmospheres had no effect on line shape below 1.5°K.

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