Infrared Study of Liquids. I. The Theory of the ir Spectra of Diatomic Molecules in Inert Solutions

Abstract

A theory is proposed to explain the ir spectra of inert solutions of diatomic molecules. The theory is a stochastic‐type theory related to similar theories of the NMRspectra. The vapor‐solution band shifts are shown to depend on the difference between the solvent–solute interaction energies of the two vibrational states involved in the transition. The band profiles are basically asymmetrical; nevertheless, symmetric limiting forms exist as well. The theory predicts the existence of a continuous sequence of band forms comprising, among others, the profile with P‐ and R‐type wings, the Lorentzian profile, the Gaussian profile, the Voigt profile, and several sorts of asymmetric profiles. The relation between a given band form and the nature of the dominating relaxation process is discussed.