EXPERIMENTAL, THEORETICAL AND NUMERICAL-STUDIES OF LINE BROADENING BYDISORDER - THE CO VIBRATIONAL TRANSITION IN SOLID ALPHA-(CO-N-2) ALLOY

Solid alpha-(CO-N-2) alloy shows a substitutional disorder and an orie ntational disorder since the CO molecules take their CO or OC orientat ion at random. This fact leads to diagonal and off diagonal disorder i n the description of the vibrational states of this molecular alloy. A simple model of crystal Hamiltonian is proposed to calculate the Rama n band shape corresponding to the 0 --> 1 vibrational transition of CO . The theoretical predictions allow a qualitative description of the l ine broadening behaviour over the full concentration range and the num erical results are in good agreement with the experimental data. The r espective influence of diagonal and off-diagonal disorder to the line broadening is also discussed.