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Reference measurements of Hydrogen's Dielectric Permittivity

Published

Author(s)

James W. Schmidt, Michael R. Moldover, Eric F. May

Abstract

We used a quasi-spherical cavity resonator to measure the relative dielectric permittivity εr of H2 at frequencies from 2.4 GHz to 7.3 GHz, at pressures up to 6.5 MPa, and at the temperatures 273 K and 293 K. The resonator was calibrated using auxiliary measurements of εr(p,T) for helium together with the accurate ab initio values of helium's dielectric permittivity. The measurements determine accurate values of hydrogen's molecular electric polarizability and its temperature dependence. At 273 K, we obtained αε,H2 = (8.9568{plus or minus}0.0008) ×10-41 F m2, which agrees with the value (8.9566{plus or minus}0.0026) ×10-41 F m2 that was obtained by combining Rychlewski's ab initio calculations with estimates of rotational level populations. (All uncertainties reported here are one standard uncertainty.) Our results yield the temperature dependence dαε,H2/dT=αε,H2×(1.1{plus or minus}0.3)×10-5 K-1, which agrees with the calculated value 1.0×10-5 K-1. Our data also determine hydrogen's second dielectric virial coefficient, bε,H2 = (0.03{plus or minus}0.05) cm3 mol-1, a property that has not yet been calculated.
Citation
Molecular Physics
Volume
107
Issue
15

Keywords

dielectric constant, dielectric permittivity, helium, hydrogen
Created August 10, 2009, Updated February 19, 2017