l-resonance perturbations in overtone and combination vibrational systems of C3ν molecules

Abstract

The problem of the l-resonance between different vibrational components of combinations and overtones in symmetric tops is considered and is examined in detail for C3ν molecules. Matrix elements are given for the general case, including vibrational states with multiple excitation of degenerate normal modes. The conditions for the splitting of rotational sublevels are also determined.As an example, the theory is applied to the ν2 + ν6, ν5 + ν6 perturbed infrared system of methyl bromide, and the computed band contour is shown to be in agreement with the experiment.