EXCITON DELOCALIZATION IN THE LIGHT-HARVESTING LH2 COMPLEX OF PHOTOSYNTHETIC PURPLE BACTERIA

Absorption and circular dichroism spectra for both long-wavelength ban ds of the antenna LH2 complex from photosynthetic purple bacteria have been calculated. Calculations were performed taking into account reso nant interactions between all 27 bacteriochlorophyll (BChl) molecules for different values of site inhomogeneity. The exciton delocalization length within BChl800 and BChl850 rings was estimated on the basis of calculated exciton wavefunctions for different temperatures and site inhomogeneity values. The relationship between anomalously high bleach ing values in pump-probe spectra and the exciton delocalization length is discussed.