Electron mobility in supercritical ethane as a function of density and temperature

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Abstract
The electron mobility is reported for ethane as a function of density at various temperatures above Tc. The high pressure cell used permits measurements to 200 atm. Our analysis shows that theory is consistent with the ethane mobility results at low and intermediate densities. At densities less than 1×1021 molecules/cm3 electrons are scattered by isolated ethane molecules and the Lorentz equation is valid. At intermediate densities, μe correlates with the square of the velocity of sound, indicating that in dense fluids the adiabatic compressibility must be included. The data are consistent with a modified Cohen–Lekner equation, and the minimum in μeN observed at densities just below dc is qualitatively accounted for by changes in the adiabatic compressibility. Thus the concept of quasilocalization, suggested by others to qualitatively explain such minima, is unnecessary here. At higher densities an additional, unspecified, scattering mechanism becomes important.