Skip to main content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.


The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

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 = (8.9568{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.
Molecular Physics


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