Theory of time dependent optical linewidths in supercooled liquids

The time resolved inhomogeneous broadened line shape is derived from analyt ical theory for a liquid which exhibits spatial heterogeneity regarding the solvent response times. The results demonstrate that it is the heterogeneo us nature of supercooled liquids which gives rise to asymmetric lines and t o a maximum in the linewidth as a function of time while the average emissi on energy experiences a redshift. The time dependence of the calculated and of the observed linewidths agree quantitatively, but differ significantly from the behavior expected for systems with homogeneous dynamics. (C) 2001 American Institute of Physics.