Photon echoes in doped organic amorphous systems over a wide (0.35–50 K) temperature range

Abstract

Optical photon echo measurements on seven doped organic amorphous systems (resorufin (Res) in D- and D 6-ethanol (EtOD and EtOD 6), tetra-tert-butylterrylene (TBT) in polyisobutylene and in polymethylmetacrylate (PMMA), zinc-tetraphenylporphine (ZnTPP) in EtOD and EtOD 6 and in PMMA) have been performed in a wide temperature range (0.35–50 K). This wide temperature interval (more than two decades) permits to clearly separate for the first time the two different contributions to the line width (optical dephasing): low-temperature broadening which follows a power law, and high-temperature broadening which demonstrates an exponential-like behavior. The values of the exponent α obtained at low temperatures in the cases of TBT and ZnTPP in PMMA matrix show some marked discrepancy with theoretical predictions, which can be attributed to a failure of the standard TLS model for a treatment of these systems or to an inaccuracy of the PMMA parameters calculated in literature. A comparison of the high-temperature part of the line broadening of different dye molecules (ZnTPP and Res), embedded in the same matrices (EtOD and EtOD 6) shows that the optical dephasing is determined by two contributions – the dynamics of matrix itself and the dynamics which is related to the doped molecules.