Nonlinear optical channels of polarizability induction in a pair of interacting molecules

Intermolecular interactions induce additional terms of polarizability of a molecular ensemble and thus allow the vibrational Raman transitions forbidden by the selection rules for isolated molecules. Based on the diagrammatic technique, a new long-range induction channel of the binary polarizability is established for which the outer field and the electric field of one molecule nonlinearly polarize the partner particle. An account for this channel is demonstrated to be crucial for an exhaustive quantitative interpretation of the СО$_2$ $\nu_3$ Raman band induced by the СО$_2$-СО$_2$ and СО$_2$-Ar collisions.