Reference measurements of Hydrogen's Dielectric Permittivity

Published

August 10, 2009

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 ε_r 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 ε_r(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 α_ε,H2 = (8.9568plus or minus}0.0008) ×10^-41 F m², which agrees with the value (8.9566plus 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 dα_ε,H2/dT=α_ε,H2×(1.1plus 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, b_ε,H2 = (0.03plus or minus}0.05) cm³ mol^-1, a property that has not yet been calculated.

Citation

Molecular Physics

Volume

107

Issue

15

Pub Type

Journals

Download Paper

Local Download

Keywords

dielectric constant, dielectric permittivity, helium, hydrogen

Citation

Schmidt, J. , Moldover, M. and May, E. (2009), Reference measurements of Hydrogen's Dielectric Permittivity, Molecular Physics, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=901652 (Accessed December 12, 2024)