Exciton dynamics in molecular aggregates

The fundamental aspects of exciton dynamics in double-wall cylindrical aggregates of cyanine dyes are studied by means of frequency resolved femtosecond pump-probe spectroscopy. The collective excitations of the aggregates, resulting from intermolecular dipole-dipole interactions have the characteristic property – the localization of the lowest lying exciton states. The experimentally observed outer-to-inner tubule excitonic energy transfer dynamics and the internal energy relaxation at low temperatures reveal a non-equilibrium population of the excitonic subsystem. The analysis of measured dynamics reveals very fast picosecond timescale energy relaxation to the optically active energy states