Higher-Order Rotation-Vibration Energies of Polyatomic Molecules. VI

Abstract

When resonance between vibration frequencies of polyatomic molecules sets in, the contact‐transformation method proposed by Shaffer, Nielsen, and Thomas is not directly applicable. It has been shown by Nielsen that a contact transformation method may still be used to advantage when computing rotation‐vibration energies to a second order of approximation, the transformation function being, however, a modified one. This problem is treated here when the question of the computation of the rotation‐vibration energies is extended to a fourth order of approximation.