Thermal conductivity and quantum diffusion in solid H2 |
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Authors: | X. Li D. Clarkson H. Meyer |
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Affiliation: | (1) Department of Physics, Duke University, Durham, North Carolina |
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Abstract: | The thermal conductivity of solid H2 and the NMR absorption signal of isolated o-H2 were measured simultaneously along isotherms 0.07<T<1.5 K as a function of time after a rapid cooldown from 2 K. The o-H2 concentration ranged from 3.4% to 0.4%, and the pressure was 90 atm. During the measurements, clustering of o-H2 particles occurred as seen from the changes both of the NMR signal amplitude and of with time t. The difference –1=–1()––1(0) between the thermal resistivity –1(t=0) just after cool down and in equilibrium, –1(), was found to change sign near 0.23 K, and this result is discussed with respect to previous experiments. The equilibrium resistivity attributed to the o-H2 impurities,, is derived and is compared with previous determinations and with predictions. An analysis of the equilibration process for –1 and for the NMR signal amplitude is presented. It shows that the characteristic times are of comparable but not equal magnitude. Comparison of the derived from NMR data atP=90 and 0 atm favors resonant ortho-para conversion over quantum tunneling as the leading mechanism for quantum diffusion. |
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