Cyclic molecular aggregates: influence of quasi-static and dynamic disorder on their excitonic line shapes

For Frenkel excitons moving on molecular rings modeling in part bacteria ph otosynthetic antenna systems we investigate the influence of static and dyn amic disorders on their optical line shape. The static disorder, describing inhomogeneities and slow motions of the protein backbone and the dynamic d isorder, simulating the influence of vibrational degrees of freedom, are ta ken into account by fluctuations of the local excitation energies of the BC hl molecules. The fluctuations are represented by dichotomic Markov process es with colored noise with different amplitudes and decay constants of the correlation functions. We obtain a closed set of equations of motion for th e correlation functions determining the optical line shape which is solved numerically. We display the optical line shapes of the circular aggregates with 9 BChls for different regimes of the exciton transfer under the influe nce of the disorders and discuss them for various sets of the model paramet ers describing static and dynamic disorders. (C) 2000 Elsevier Science B.V. All rights reserved.