Third order determination of the vibrational spectroscopic constants for a triatomic linear molecule affected by Fermi resonance

Abstract

For a molecule affected by Fermi resonance, we establish, up to third order of approximation, the general formulae relating the spectroscopic constants to the mean value of the vibrational energy (in any Fermi polyad) and to the spacings of vibrational energy levels (in a Fermi diad or a Fermi triad).