Intermolecular Coupling of Vibrations in Molecular Crystals. II. Intermolecular Forces in CH3Cl and CD3Cl

Abstract

The effect of isotope substitution on band splittings caused by dipole coupling between molecules is examined. For methyl chloride and methyl bromide, the results support the contention that the theory of dipole coupling in its present form is not sufficient to explain the splittings in most bands. The theory of atom‐atom interactions presented in part I of this series is applied to various possible potentials coupling the motions of normal and deuterated methyl chloride molecules. A repulsive potential acting between hydrogen atoms of neighboring molecules accounts for the splittings of several bands. Certain types of coupling potentials seem ruled out by the results of these calculations, while others are left as possible factors in band shifts which occur when a gas is condensed.