OBSERVATION OF FAST TIME SCALE SPECTRAL DIFFUSION IN A LOW-TEMPERATURE GLASS - COMPARISON OF PICOSECOND PHOTON AND STIMULATED ECHOES

Results of temperature-dependent two-pulse photon echo and three-pulse stimulated echo experiments on an organic dye (rhodamine 101) in a polymer glass (PMMA) are presented. Decay rates at a fixed temperature are shown to increase as the waiting time, T(W) (time between the second and third pulse) of the stimulated echo increases. This is due to spectral diffusion caused by structural relaxations of the host. At a fixed waiting time, decay rates follow a power law dependence on temperature which is characteristic of the glassy state. The data are analyzed by explicitly evaluating the stimulated echo correlation function for short T(W).