SIGNATURES OF THE GLASS-TRANSITION IN A VAN-DER-WAALS LIQUID SEEN BY NEUTRONS AND NMR

Mode coupling theory (MCT) of the glass transition predicts the existence of a dynamic anomaly of supercooled liquids at a characteristic temperature T(c) well above the caloric glass transition temperature T(g). A series of neutron scattering and NMR experiments on van der Waals liquids - a typical example of which is orthoterphenyl (OTP) - have been performed to test three predictions and to point out signatures of the glass transition. This contribution is meant to review our results in a concise manner: there is strong evidence for a T(c) according to MCT from Debye-Waller factors, from line shape studies of the dynamic structure factor and from a comparison of self-diffusion and viscosity. NMR relaxation below T(c) shows that there is at least one secondary process which so far is not accounted for by MCT and that the supercooled liquid becomes truely nonergodic closely above T(g) on a time scale of a few seconds.