We developed a model to mimic the exciton dynamics in J-aggregates of cyani
ne dyes on the basis of Monte Carlo simulations. We consider the aggregates
to be linear one-dimensional chains, where the in-phase combination of mol
ecular excitons leads to a stabilization. A random distribution of segment
lengths limits the effective coherence length and induces an inhomogeneous
band broadening. The model takes into account the incoherent energy hopping
between aggregates following the excitation. The results of the simulation
could be fitted to the experimentally obtained absorption and fluorescence
spectra and to the fluorescence decays of the J-aggregates of 3,3'-disulro
propyl-5,5'-dichloro-thiacarbocyanine (THIATS).