Evidence for Dynamic Heterogeneity near Tg from the Time-Resolved Inhomogeneous Broadening of Optical Line Shapes

The temporal evolution of inhomogeneous spectra emitted by dye molecules in the course of their solvation within a supercooled liquid is analyzed, where the average emission energy ν( t ) probes the dielectric relaxation. The observed increase in the optical line width, σ inh ( t ), near the glass transition is compared to corresponding simulations under the conditions of spatially heterogeneous and homogeneous solvation dynamics. From this data on higher moments of the relaxing quantity, we conclude on the spatial variation of relaxation times.