Heterogeneous large amplitude atomic motion in supercooled liquids

One of the central questions in glass physics is the dynamic nature of the glass transition. Essential issues are the type of atomic motions involved and their homogeneity or heterogeneity. Previous experimental studies of the dynamic heterogeneity performed by special NMR techniques for times >10(-6) s and by incoherent neutron scattering were restricted to the alpha-relaxation process. Here we review the results of neutron scattering studies focused on the picosecond time domain showing that fast beta-process corresponds to large amplitude cluster like heterogeneous motion. (C) 2003 Published by Elsevier Science B.V.