Band shapes of infrared absorption spectra of isotopically diluted XH groups in hydrogen-bonded crystals

Abstract

A model is proposed which quantitatively describes the infrared band shapes of the stretching vibrations of isotopically diluted XH groups in hydrogen-bonded crystals. The model assumes weak interactions between the high-frequency XH stretching vibration and low-frequency vibrations of the lattice. The interactions are described in the adiabatic approximation and an expression is obtained which yields band shapes at different temperatures. The model explains the observed experimental facts such as symmetric band shapes, changes of band shapes and widths with temperature, the isotopic effect and the absence of sidebands in infrared spectra.