OPTICAL-DYNAMICS IN MONODIMENSIONAL AGGREGATES WITH EXCITON-PHONON COUPLING - A NUMERICAL INVESTIGATION ON THE TIME-EVOLUTION OF THE OPTICAL DOORWAY STATE

A numerical technique based on the Lanczos tridiagonalization procedure is shown to be suitable for investigating the time evolution of the optical doorway state in model systems exhibiting exciton-phonon coupling. Taking as an example a five-site ring (one harmonic oscillator per site) with site-diagonal exciton-phonon coupling, we present and discuss some results concerning the motion of the vibrational wavepacket in each oscillator, the (time-dependent) delocalization energy for the exciton and the Raman spectra. The numerical results are also used to test the validity of a time-dependent variational approach, which, when appropriate, requires a minor computational effort.