Thermal conductivity and accommodation coefficient of spin-polarized atomic-hydrogen gas.

Abstract

The thermal conductivity of a spin-polarized atomic-hydrogen gas and its accommodation coefficient on saturated superfluid $^{4}\mathrm{He}$ films have been determined experimentally using a cell comprised of coaxial cylinders. The thermal conductivity was measured for temperatures 0.3T0.4 K and for magnetic fields 4.00H7.00 T. The value of the thermal conductivity for spin-polarized hydrogen is 3\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}3}$ W/K m for T=0.3 K and H=7.00 T. The measured thermal conductivity is independent of the applied magnetic field, and its magnitude and temperature dependence are in agreement with ab initio calculations for a paramagnetic Bose gas model. No evidence for anomalous transport due to thermal fluctuations in the gas magnetization has been observed. The accommodation coefficient for spin-polarized hydrogen upon saturated superfluid $^{4}\mathrm{He}$ films for 0.2T0.4 K and 3.00H7.00 T was found to be independent of the applied magnetic field and to be given by the expression ${\mathit{a}}_{\mathit{c}}$=(0.56\ifmmode\pm\else\textpm\fi{}0.06)T. This value is in agreement with previous measurements of the accommodation and sticking coefficients.