Abstract
We report on the optical dynamics in aggregates of pseudoisocyanine (PlC) bromide and iodide and 5 chloride (TCCC1). For PlCBr in an ethylene glycol/water glass we discuss the results of resonance light scattering (RLS) timeresolved emission and photon echo decay measurements. The results show that the Jaggregate absorption can be described best as a disordered Frenkel exciton band in which pseudolocalized states exist. Computer simulations of the line shape of the Jband based on Anderson''s Hamiltonian with uncorrelated diagonal site energies show that the ratio of the disorder parameter ci over the nearestneighbour coupling parameter V is about 0. 11. Using the frequency dependence of the ratio fluorescence over Raman as a probe we have also examined the dephasing process and derived parameters for the bath correlation function at three different temperatures. It is shown that at all temperatures the exciton dephasing process occurs in the fast modulation limit. For PlC in a LangmuirBlodgett (LB) film the optical excitation can be described also in terms of a band transition but the disorder is much larger than in a glass. The lowtemperature fluorescence lifetime in a PlC bilayer of about 10 picoseconds suggests that in this twodimensional structure the optical excitation is much more delocalized than in the selforganized aggregates in a glass. We report also on the spectroscopy of TCC in LB films.
Published Version
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