| Abstract
| - A theoretical description of femtosecond two-dimensional electronic spectroscopy of multichromophoric systemsis presented. Applying the stationary phase approximation to the calculation of photon echo spectra and takinginto account exciton relaxation processes, we obtain an analytic expression for numerical simulations of time-and frequency-resolved 2D photon echo signals. The delocalization of one-exciton states, spatial overlapsbetween the probability densities of different excitonic states, and their influences on both one- and two-dimensional electronic spectra are studied. The nature of the off-diagonal cross-peaks and the time evolutionof both diagonal and off-diagonal peak amplitudes are discussed in detail by comparing experimentally measuredand theoretically simulated 2D spectra of the natural Fenna−Matthews−Olson (FMO) photosynthetic light-harvesting complex. We find that there are two noncascading exciton energy relaxation pathways.
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