ISSN:
1573-7357
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract The thermal conductivity κ 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 κ with time t. The difference Δκ −1 =κ −1 (∞)−κ −1(0) between the thermal resistivity κ −1 (t=0) just after cool down and in equilibrium, κ −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, $$\kappa _{o - H_2 }^{ - 1} $$ , is derived and is compared with previous determinations and with predictions. An analysis of the equilibration process for κ −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 τ derived from NMR data atP=90 and 0 atm favors resonant ortho-para conversion over quantum tunneling as the leading mechanism for quantum diffusion.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00683315
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