SPECTRAL HOLE-BURNING IN POLYMORPHIC SYSTEMS - SINGLE-SITE PRESSURE PHENOMENA AND GLASSY BEHAVIOR

We measured the pressure-induced shift and broadening of spectral hole s for 14 different impurity sites in a polycrystalline solid solution of chlorin (17,18-dihydro-21H,23H-porphine) in benzophenone. In additi on, we investigated the glassy phase of the same system in a frequency range which covered the entire inhomogeneously broadened band. The te mperature range of the experiments was between 1.5 and 4.2 K. Pressure levels up to 10 MPa were applied. In the glassy phase, we observed a linear frequency dependence of the shift per pressure. However, in the crystalline phase, the general trend of the data clearly indicated a nonlinear frequency dependence. Yet, the individual sites, especially those with lower frequencies, showed a kind of stochastic scattering a round the general trend behavior. Tle results were interpreted within the frame of existing models. The experiments demonstrate that matrix isolation combined with hole burning spectroscopy of large molecular i mpurities in polymorphic host materials under varying pressure conditi ons is a useful technique for determining molecular as well as bulk pa rameters, for examining problems of microelasticity and microplasticit y, and for investigating the fundamental differences between glasses a nd crystals.