Light harvesting complex LH2 - simulation of spectral profiles

Abstract

Absorption and steady state fluorescence spectra are simulated for relatively simple circular molecular system. It can be treated as a model of peripheral light harvesting complex LH2 from purple bacterium Rhodopseudomonas acidophila. Both rings (B850 ring and B800 one) are included in our model. The spectra are calculated within full Hamiltonian model and compared for two types of slow fluctuations. Gaussian fluctuations in local excitations energies and Gaussian fluctuations in positions of bacteriochlorophylls are considered. Fast fluctuations, interaction with phonon bath, is also taking into account for low and room temperature. The resulting spectra show strong dependence on temperature. Splitting of both spectra are visible at low temperature. The differences caused by static disorder type are also remarkable. Localization of exciton states contributing to the steady state fluorescence spectra is investigated by thermally averaged participation ratio.