Intermolecular Potentials from Dielectric Polarization in Polar Gases

A theory which relates the dielectric polarization of polar gases to the intermolecular potential is formulated. In it occurs an expansion in powers of 1/V, analogous to the virial expansion. The convergence of this series is briefly discussed, and the impossibility of rotational transitions in the gas phase is shown. Evaluation is limited to the leading term of the expansion, which involves interactions of a pair of molecules only and which is calculable from a knowledge of the intermolecular potential. Various intermolecular potentials consistent with virial data are introduced, and the results are compared with experiment for ammonia, methyl fluoride, and hydrogen fluoride. In view of the unsatisfactory precision of the experimental data, the agreement is as good as can be expected and is qualitatively in agreement with previous concepts of the strength and nature of the hydrogen bond.