Infrared Spectra of the Hydrogen-Bonded Carboxylic Acids

Abstract

The condition of separability of different vibrational modes in dimers of carboxylic acids is analyzed. In the excited vibrational state the OH stretching modes are intrinsically coupled with the hydrogen-bond vibrations and can be separated only in limiting cases. The physical nature of this coupling is studied and for a simplified model of carboxylic acid dimer the fundamental Hamiltonian describing this coupling is derived. The formulas for the bandwidth, center of gravity, and total intensity of the infrared absorbtion spectrum are obtained.