Local and nonlocal contributions to the linear spectroscopy of light-harvesting antenna systems

In this gaper the circular dichroism and absorption spectra of the LH2 comp lex of Rhodopseudomonas acidophila, for which the atomic structure is known , are analyzed. We show that an analysis based on the distribution of the e xcitations in real space, and their correlations, to unravel the relation b etween the atomic structure of the light-harvesting complex and its exciton ic properties, is particularly successful. Starting from molecular expressi ons for the linear susceptibility, we demonstrate that linear spectra can b e viewed as originating from the product of coherence correlation functions and geometric structure factors. Effects of homogeneous and inhomogeneous broadening can be incorporated in a natural way and lead to a definition of exciton length as the distance over which coherence correlation functions decay.