HOMOGENEOUS LINE WIDTHS IN GLASSES IN THE FRAMEWORK OF A SOFT POTENTIAL MODEL

The temperature dependence of the optical line width of an impurity em bedded in a glass matrix is investigated. A model Hamiltonian which co uples the impurity to the characteristic soft modes of the glasses in the phonon field of the matrix is introduced. We find an excellent agr eement between our model predictions and experimental data. We are als o able to reproduce supralinear behaviors in low-temperature regime wi thout any adjustable parameter for the density of states. Finally, the quadratic behavior extending to very low temperatures is explained in terms of the Bose Peak equivalent temperature.