Direct Measurements of the Dielectric Virial Coefficients of ^{4}He between 3 K and 18 K
Abstract
The second and third dielectric virial coefficients of ^{4}He have been measured by the symmetrical gasexpansion technique of Buckingham, Cole and Sutter for six isotherms between 3,00 K and 17,68 K. The effects of helium adsorption are important, and are considered in detail. No temperature dependence of the second coefficient is seen at a level of δb=+/0,008 cm^{3} mol^{1}, and average values of the second and third coefficients are b = 0,006 (10) cm^{3} mol^{1} and c = 5 (4) cm^{6} mol^{2}, respectively. The uncertainty for b is relatively large because it has a systematic dependence on c: reanalysis of all the existing data shows that a more probable value of the third coefficient is c = 2 (1) cm^{6} mol^{2}, which when combined with our data gives b (3 K  18 K) = 0,001 (4) cm^{3} mol^{1}. The very small value suggests that theoretical calculations of the excess polarizability of the helium diatom need to be reconsidered. The small value and the small uncertainty of b indicate that future work to improve experimental values of the second density virial coefficient of ^{4}He for this temperature range may without ambiguity make use of the methods of dielectric constant gas thermometry.
 Publication:

Metrologia
 Pub Date:
 January 1992
 DOI:
 10.1088/00261394/29/1/006
 Bibcode:
 1992Metro..29...37W