Theory of pressure shifts of HCl lines caused by noble gases

Abstract

Abstract Recent experimental work has shown that the shift of lines in the 1-0 and 2-0 bands of HC1, when absorbed under perturbation by rare gases, is strongly dependent on the rotational quantum number. To explain this effect, we calculate the forces between a rotating and vibrating dipole and a spherically symmetric atom, retaining the influence of space quantization. It is also indicated why space quantization of the dipole with respect to the interaction line matters in this problem. Asymptotic dispersion forces do not account for the results observed, nor should this be expected. But when repulsive forces are included, many experimental features, especially the J-dependence of the shifts, receive at once a qualitative explanation. In part V of this article, two models, one very crude and one more realistic, are employed in an attempt to account for the numerical shifts. The work necessarily involves the use of unknown kinetic theory parameters. Fitting the data leads to their determination; not incontrovertibly to be sure, but in a manner that leaves little doubt as to the basic adequacy of the explanation offered.