Affiliation:
1. National Institute of Standards and Technology, Physical Measurement
Laboratory, Gaithersburg, MD 20899, USA
Abstract
Measurements of the relative permittivity (static dielectric constant) of fluids
such as methane have been interpreted with the assumption of zero dipole moment.
This assumption is not strictly true, due to the presence of isotopologues with
small, nonzero dipole moments. We investigate the significance of this effect by
analyzing the effect of the dipole of CH3D on the static dielectric constant of
methane. It is found that the isotopologue effect is more than two orders of
magnitude smaller than the uncertainty of the best existing measurements. Similar
estimates for other compounds such as H2 and CO2 produce even smaller effects.
Therefore, the interpretation of these measurements with a dipole moment of zero
remains valid.
Funder
Physical Measurement Laboratory
Publisher
National Institute of Standards and Technology (NIST)