Resonance dipole–dipole interactions are shown to strongly manifest themselves in fundamental and overtoneband shapes of low-temperature systems, consisting of polar and nonpolar molecules as well with a relativelylarge first derivatives (P′ > 0.3 D) of the dipole moment. The rough model on the basis of the interaction between two non-degenerate, doubly degenerate, and triply degenerate oscillators was developed to study pairs ofinteracting molecules and clusters in low-temperature condensed systems. The concentration dependences ofsecond- and third-order spectral band moments permitted the number of molecules in clusters to be estimated.