Relaxation, rattling and decoupling

Glass is a material of paramount importance. It is ubiquitous in everyday life and used in classical fields as packaging, household or architecture. In addition it can be applied in more recent fields like optical fibres in communication techniques, lenses in high-resolution microscopes or as bioactive implants in medicine. Despite its importance, the physics of glasses is only poorly understood and the transition from the liquid to the glassy state is still considered as one of the great unsolved problems in solid state physics. Dielectric spectroscopy is proven to be a very powerful tool for the investigation of the dynamic behaviour of glassy matter in a very broad frequency range. It reveals a whole zoo of dynamic processes: the structural -relaxation, the excess wing and the slow -relaxation, the minimum regime and the boson peak. The present work provides information on all these processes in a series of different molecular glass-formers in the whole frequency range accessible. For the first time systematic studies on the behaviour of the fast -process and the boson peak are performed. These allow for testing several phenomenological models and theories of the dynamics of supercooled liquids.