Ultrafast IR Spectroscopy Reveals the Structural and Dynamical Heterogeneity in Glassy Materials

Speaker:  David J. Hoffman, Stanford University

Program Description:
The remarkable properties of glassy materials arise from their complex amorphous structures and dynamics. The heterogeneity of these materials was studied on molecular length scales and picosecond time scales using a combination of polarization-selective IR pump-probe and 2D IR experiments and a vibrational chromophore that is sensitive to local chemical and electrical environments. By monitoring the restricted orientational motion of the chromophore in a polymer, the distribution of sub-nanometer pores could be explored. The same chromophore in a hydrogen-bonding system showed extreme polarization dependence in the 2D line shape, providing evidence for significant dynamical heterogeneity in the supercooled liquid phase.