Estimation of the spectral density function of LH2 complexes from the temperature dependence of the absorption spectra

The spectral density function of a bacteriochlorophyll molecule in its parametric form describing the exciton coupling to the vibrational bath including the protein and the solvent modes has been determined.This form of spectral density is applied by simulating the temperature dependence of the absorption spectra of the peripheral light harvesting complexes, LH2, of the photosynthetic purple bacterium Rhodobacter sphaeroides inserted into the polyvinyl alcohol film.It has been found that the dynamic characteristics of broadening of both absorption bands of LH2 with the maxima at 850 nm and 800 nm are similar to those already obtained for the glycerol solution.The static spectral inhomogeneity of LH2 in the polyvinyl alcohol film, however, is much larger than in the glycerol solution.It is concluded that the LH2 complex in the polyvinyl alcohol film with increase of the temperature is subjected to compression, which is the source of the additional static disorder.