Electron Relaxation and Molecular Vibrations: Triatomic Systems of the First-Row Elements, the Methyl Radical, and Diazomethane and Ketene

Abstract

The well-known second-order perturbation method is used to correlate the bond–bond interaction constants in ground and excited electronic states of triatomic systems of the first-row elements, and unusual force constants in diazomethane and ketene with the effect of electron relaxation. The third- and fourth-order perturbation schemes are used to determine qualitatively the contributions to the third- and fourth-order parts of the vibrational potential function of carbon dioxide, by the electron relaxation effect. The fourth-order theory is used to rationalize the negative anharmonicities observed in ketene, diazomethane, the methyl radical, and planar excited states of ammonia.