Reference measurements of hydrogen's dielectric permittivity

We used a quasi-spherical cavity resonator to measure the relative dielectric permittivity εr of H2 at frequencies from 2.4 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 [image omitted] = (8.9568 ± 0.0008) × 10-41 F m2 (all uncertainties reported here are one standard uncertainty), which agrees with the value (8.9566 ± 0.0026) × 10-41 F m2 that was obtained by combining Rychlewski's ab initio calculations with estimates of rotational level populations. Our results yield the temperature dependence [image omitted] = [image omitted] × (1.1 ± 0.3) × 10-5 K-1, which agrees with the calculated value [image omitted] × 1.0 × 10-5 K-1. Our data also determine hydrogen's second dielectric virial coefficient, [image omitted] = (0.03 ± 0.05) cm3 mol-1, a property that has not yet been calculated. [ABSTRACT FROM AUTHOR] Copyright of Molecular Physics is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)