Low-Temperature Specific Heats of Solid Neon and Solid Xenon

The specific heats of solid neon and xenon have been measured in the temperature range 1.5 to 24\ifmmode^\circ\else\textdegree\fi{}K, using a calorimeter with a mechanical heat switch. Carbon resistance thermometers were calibrated against a gas thermometer and the helium vapor-pressure scale. The results were analyzed to obtain the temperature dependence of the Debye temperature, ${\ensuremath{\Theta}}^{c}(T)$. In the range $0.020\ensuremath{\lesssim}\frac{T}{{{\ensuremath{\Theta}}_{0}}^{c}}\ensuremath{\lesssim}0.505$, the data were fitted with an expression of the form ${\ensuremath{\Theta}}^{c}(T)={{\ensuremath{\Theta}}_{0}}^{c}+A{T}^{2}$, where ${{\ensuremath{\Theta}}_{0}}^{c}$ is the Debye temperature at 0\ifmmode^\circ\else\textdegree\fi{}K. This procedure gave ${{\ensuremath{\Theta}}_{0}}^{c}=74.6\ifmmode\pm\else\textpm\fi{}1.0$\ifmmode^\circ\else\textdegree\fi{}K for neon and ${{\ensuremath{\Theta}}_{0}}^{c}=64.0\ifmmode\pm\else\textpm\fi{}0.8$\ifmmode^\circ\else\textdegree\fi{}K for xenon. The results for ${\ensuremath{\Theta}}^{c}(T)$ are compared with the calculations of Bernardes, Horton, and Leech, and Barron and Klein, based on Mie-Lennard-Jones potentials for the interaction energy between two atoms. Tables of the following smoothed thermodynamic properties between 1.0 and 24\ifmmode^\circ\else\textdegree\fi{}K are given in Table I: specific heat at constant pressure, specific heat at constant volume, entropy, and enthalpy.

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