Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Reference measurements of Hydrogen's Dielectric Permittivity



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


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 = (8.9568plus 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 dαε,H2/dT=αε,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, bε,H2 = (0.03plus or minus}0.05) cm3 mol-1, a property that has not yet been calculated.
Molecular Physics


dielectric constant, dielectric permittivity, helium, hydrogen


Schmidt, J. , Moldover, M. and May, E. (2009), Reference measurements of Hydrogen's Dielectric Permittivity, Molecular Physics, [online], (Accessed April 18, 2024)
Created August 9, 2009, Updated October 12, 2021