Optical homogeneous linewidths in glasses in the framework of the soft-potential model

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Abstract
The temperature dependence of the optical linewidth of an impurity embedded in a glass matrix is investigated. A model Hamiltonian that couples the impurity to the soft modes characteristic of glasses in the phonon field of the matrix is introduced. We find an excellent agreement between our model predictions and experimental data. We are also able to reproduce supralinear behaviors in the low-temperature regime without 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.