Low-temperature Viscosity Cross Sections Measured in a Supersonic Argon Beam II

Abstract

In an earlier study,¹ values of the thermal-conductivity (viscosity) cross section for argon deduced from velocity distributions measured near the centerline of a free jet deviated unexpectedly from the temperature dependence predicted for low temperatures. Subsequently, the molecular-beam sampling system and data-reduction procedures used in that study were upgraded and the measurements were repeated. Cross-section values were obtained at temperatures more than an order of magnitude below the normal condensation temperature of argon. The temperature dependence of the deduced effective hard-sphere diameter is in good agreement with the predicted dependence, but the magnitudes are about 10 percent less then the predicted values.