Liu, QihanHuang, ShichengSuo, Zhigang2017-02-212015Liu, Qihan, Shicheng Huang, and Zhigang Suo. 2015. “Brownian Motion of Molecular Probes in Supercooled Liquids.” Physical Review Letters 114 (22) (June 4). doi:10.1103/physrevlett.114.224301.0031-9007http://nrs.harvard.edu/urn-3:HUL.InstRepos:30403687When a supercooled liquid approaches glass transition, viscous flow slows down greatly, but often the Brownian motion of a molecular probe in the host liquid does not slow down as much, causing the Stokes-Einstein relation to fail by orders of magnitude. Here we formulate a theory that relates the Brownian motion of the probe to two concurrent processes in the host liquid: viscous flow and molecular hopping. Molecular hopping prevails over viscous flow when the probe is small and the temperature is low. Our theory generalizes the Stokes-Einstein relation and fits the experimental data remarkably well.en-USJournal Article2017-02-2110.1103/PhysRevLett.114.224301