KubarychGroup
J. T. King, M. R. Ross, K. J. Kubarych, Phys. Rev. Lett. 108 (2012) 157401
Ultrafast two-dimensional infrared (2D-IR) spectroscopy is used to study the picosecond dynamics of a vibrational probe molecule dissolved in a fragile glass former. The spectral dynamics are observed as the system is cooled to within a few degrees of the glass transition temperature (Tg). We observe non-exponential relaxation of the frequency-frequency correlation function, similar to what has been reported for other dynamical correlation functions. In addition, we see evidence for α-like relaxation, typically associated with long-time, cooperative molecular motion, on the ultrafast timescale. The data suggests that the spectral dynamics are sensitive to cooperative motion occurring on timescales that are necessarily longer than the observation time.
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