Spectral Line Shape of High-Frequency Local Vibrations in Adsorbed Molecular Lattices

We consider high-frequency local vibrations anharmonically coupled with low-frequency modes in a planar lattice of adsorbed molecules. The effect of lateral intermolecular interactions on the spectral line shape for local vibrations is analyzed in the limit of the high density of adsorbed molecules. It is shown that the spectral line positions and widths depend on behaviour of low-frequency distribution function for a system of adsorbed molecules. The results obtained allows the spectral line characteristics of the local vibrations for isotopically diluted {$^{13}$}C{$^{16}$}O{$_{2}$} molecules in the {$^{12}$}C{$^{16}$}O{$_{2}$} monolayer on the NaCl(100) surface to be described in agreement with the experimentally measured values.