Excitonic optical line shapes of cyclic and elliptically deformed molecular aggregates with 18 units: influence of quasi-static and dynamic disorder

Abstract

We investigate the influence of dynamic and static disorder on the optical line shape of Frenkel excitons moving on molecular rings, modeling bacteria photosynthetic antenna systems. The dynamic disorder, describing the influence of vibrational degrees of freedom, and the static disorder are taken into account by fluctuations of the local excitation energies of the BChl molecules. The fluctuations are represented by dichotomic Markov processes with colored noise with different amplitudes and decay constants of the correlation functions. We obtain a closed set of equations of motion for the correlation functions determining the optical line shape, which is solved numerically. We show optical line shapes of the circular aggregates with 9 and 18 BChls for different regimes of the exciton transfer under the influence of the fluctuations taking into account also a possible elliptical deformation of the ring. The line shapes are discussed for various sets of the model parameters describing static and dynamic disorders taking into account also the possible elliptical deformation of the ring. We compare our results with the experimental data.