Line broadening by diagonal disorder in the vibrational transition of CO in solid α-CO

Abstract

Solid α-CO shows an orientational disorder since the individual molecules take their CO or OC orientation at random. In the description of the excited states this fact gives rise to diagonal and off-diagonal disorder. For vibrational transition either with Δυ > 2 or for CO isotopes diluted in CO the experimental line width can be taken as a measure of the line broadening due to the diagonal disorder alone. A simple model is proposed and theoretical results are compared with measured line widths.