Slow secondary relaxation in a free-energy landscape model for relaxation in glass-forming liquids

Within the framework of a free-energy landscape model for the relaxation in supercooled liquids the primary (alpha) relaxation is modeled by transitio ns among different free-energy minima. The Secondary (beta) relaxation then corresponds to intraminima relaxation. We consider a simple model for the reorientational motions of the molecules associated with both processes and calculate the dielectric susceptibility as well as the spin-lattice relaxa tion times. The parameters of the model can be chosen in a way that both qu antities show a behavior similar to that observed in experimental studies o n supercooled liquids. In particular we find that it is not possible to obt ain a crossing of the time scales associated with alpha and beta relaxation . In our model these processes always merge at high temperatures and the cr process remains above the merging temperature. The relation to other model s is discussed.