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Publication Citation: The Polarizability of Helium and Gas Metrology

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Author(s): James W. Schmidt; R Gavioso; E May; Michael R. Moldover;
Title: The Polarizability of Helium and Gas Metrology
Published: June 22, 2007
Abstract: Using a quasi-spherical, microwave cavity resonator, we measured the refractive index of helium to deduce its molar polarizability Aε in the limit of zero density. We obtained (Aε,meas - Aε,theory)/Aε = (-1.8{plus or minus} 8.4)× 10-6, where the standard uncertainty (8.4 ppm) is factor of 3.6 smaller than that of the best previous measurement. If the theoretical value of Ae is accepted, these data determine a value for the Boltzmann constant that is only (1.8 {plus or minus} 8.4) ppm larger than the accepted value. Our techniques will enable a helium-based pressure standard and measurements of thermodynamic temperatures.
Citation: Physical Review Letters
Volume: 98
Issue: 06/22/07
Pages: pp. 254504-1 - 254504-4
Keywords: Boltzmann constant;dielectric constant;fundamental constant;helium;index of refraction;microwave resonator;polarizability;pressure standard;temperature standard
Research Areas: Measurement Standards, Gas Metrology, Physical Properties, SI (Thermodynamics Units), Standards, Chemical Engineering & Processing, Chemistry, Fluids, Thermodynamics