9. General information on the relaxing mobility of lens formers

The specific features of glass formation and the glassy state do not lie in changes to the structural properties of the liquid, which change little in the vicinity of T _g . On the other hand, glass formers are differentiated by the specific characteristics of the dynamics of their molecules. While the nature of the thermodynamic manifestation of the glass transition is well understood, the same cannot be said of the temperature evolution of molecular mobility, involved in relaxation processes, whether on cooling, approaching T _g or for T < T _g , in the glassy state. Molecular mobility is revealed experimentally by the way in which a characteristic quantity of the system "relaxes" over time after perturbation.