Numerical calculations of optical lineshapes for disordered molecular aggregates

Numerical calculations of optical lineshapes are performed for molecular aggregates with Gaussian diagonal disorder. A method is proposed that significantly increases the efficiency of numerical calculations by choosing the fluctuating average value of transition energies of all molecules in the aggregate as an origin of the energy scale. Using the proposed method, the absorption line half-width and the exciton coherence length are examined as functions of the number of molecules in the aggregate, the degree of disorder and the disorder correlation over a wide range of parameters.