Infrared spectral moment and molecular multipoles in collision-induced absorption

Abstract

An extension and generalization of the theory of multipolar interaction is developed which includes the effects of anisotropic polarizability, anisotropic pair distribution function, and orientational correlations. A formulation of overlap interaction is evaluated using a simple inverse power-law model. The spectral integral and the first moment of the absorption coefficient α(ω) are computed for a multicomponent gas. Anisotropic 'interference' terms couple the multipolar components so that the expressions are not simply sums over individual multipolar contributions. The theory presented here has been successfully applied in earlier published work to the determination of the multipole moments and molecular parameters of linear and tetrahedral molecules.