Methods are outlined for the numerical simulation of the optical spectra of Frenkel excitons in disordered systems. The absorption line shape is expressed as a Fourier sine transform of a linear combination of Green’s functions which are calculated by integration of the microscopic equations of motion characterizing the dynamics of a finite array of optically active centers. Two examples are studied in detail: inhomogeneous broadening, arising from a Gaussian distribution of transition frequencies, and absorption in systems with a random distribution of optically inactive impurities. The results of the simulation are compared to approximate analytic calculations. In addition to testing approximate theories under controlled conditions, numerical simulations carried out with realistic Hamiltonians can be used to infer microscopic interactions by adjusting the parameters of the Hamiltonian so as to obtain agreement between simulation and experiment.

• Received 3 October 1988

DOI:https://doi.org/10.1103/PhysRevB.39.8652