Article

Ultrafast α-like relaxation of a fragile glass-forming liquid measured using two-dimensional infrared spectroscopy.

Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, USA.
Physical Review Letters (impact factor: 7.37). 04/2012; 108(15):157401. pp.157401
Source: PubMed

ABSTRACT 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 (T(g)). We observe nonexponential 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 time scale. The data suggests that the spectral dynamics are sensitive to cooperative motion occurring on time scales that are necessarily longer than the observation time.

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Keywords

cooperative molecular motion
 
cooperative motion
 
dynamical correlation functions
 
fragile glass former
 
frequency-frequency correlation function
 
glass transition temperature
 
time scales
 
ultrafast time scale
 
Ultrafast two-dimensional infrared
 
vibrational probe molecule
 
α-like relaxation
 

John T King