Dielectric Constants of Imperfect Gases. I. Helium, Argon, Nitrogen, and Methane

Abstract

Measurements from 1 to 100 atm have been made at one or more temperatures between —30° and 70°C by a special transformer ratio arm bridge operating at 10 kc; derived values of the Clausius-Mossotti function are of sufficient precision (0.1%) to justify comparison with theoretical pair fluctuation, polarizability and multipole moment interaction effects at higher densities. Helium shows a decrease of 0.3% and argon an increase of 0.1% in C-M at 100 atm, while nitrogen and methane show somewhat larger positive effects, especially at lower temperatures. A decreased effective polarizability of atom pairs at small distances is discussed as a possible explanation of the data for helium and argon, while the effect in nitrogen is consistent with quadrupole-induced dipole moments of pairs. A theory of octupole-induced dipole interactions is shown to be capable of explaining the methane results with plausible estimated values of the octupole moment.

Relative permittivities and dielectric virial coefficients of nitrogen at T= 300 K

“…Their B ε at T = 298.15 K was 0.88 cm 6 · mol −2 smaller than our value but this difference was much less than the uncertainty in our result. The greater differences between our A ε and those of Johnston et al (24) may be explained by their use of different density data to that used in this work or some unidentified systematic error in their method, but their B ε values are in very good agreement with ours.…”

Correction to the Clausius–Mosotti equation: The dielectric constant of nonpolar fluids from Monte Carlo simulations

“…The non-ideality of the charge distribution of the molecule is probably an important issue that captured the attention of several researchers over the years who modified the KY theory by including quadrupole [28][29][30][31][32][33][34][35] and octopole moments 36 . All these authors conclude that the effect of higher order terms is not negligible (supported by the experimental result that the correction is larger for CO 2 than for Ar).…”

“…The results were fitted to theories and higher order multipole moments were estimated. 4 42 were computed on the basis of the theory of Johnston et al 36 . All these measurements, nevertheless, were conducted for relatively low densities where the underlying theories can be assumed to be valid.…”

High voltage capacitors for low background experiments

“…For a 1 nF capacitor, the area of the conducting planes must be approximately 22.5 cm 2 . When operated in liquid nitrogen or liquid argon the relative permittivity, 1.44 and 1.54 respectively [5], will modify this estimate. This effect can be minimized by wrapping the foils tightly to one another.…”

“…A commercial capacitor 5 was also screened to serve as a reference for what cleanliness is available off-the-shelf. The commercial capacitor is a 1.2 nF NP0 type capacitor with a maximum operating voltage of 5 kV.…”