Single molecules in a glassy matrix reorient in abrupt hops, indicating sudden, local, rearrangement events of the glass. Averaged over many events, we recover typical glass dynamics features, such as non-exponential relaxation and dramatic temperature dependence of correlation times. We identify the times of these individual jumps of the probe molecule from the photon trajectory, representing the glass dynamics as a sequence of local relaxation events. From the sequence of waiting times we determine the lifetime of heterogeneities as smaller than 3-times the structural relaxation time. The waiting time distributions indicate that a small number of increasingly long waiting times is responsible for the slowdown of the dynamics at the glass transition. We observe sudden rearrangements with similar waiting time distributions also in molecular dynamics simulations of glass formers. The distribution of individual relaxation events in space and time agrees with predictions from a new model for glass dynamics.

Glass dynamics through sudden, local rearrangement events

244th National Meeting (2012)

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