ABSTRACT
Fundamental aspects of 2D photon echo-type spectroscopy have been discussed in detail, where the effects from chromophore-bath interactions, electronic couplings between chromophores, excitation transfer process, coherence quantum beats, and chemical exchange processes on the frequency distributions, shapes, and amplitudes of diagonal and cross-peaks. When a given pair of singly excited states are energetically close to each other so that the frequency resolution is not perfect, the crosspeaks cannot be easily identified due to the spectral congestion problems. Then, it is not always straightforward to quantitatively estimate the cross-peak amplitudes to extract information on structure and dynamics of coupled multi-chromophore systems. In this regard, the polarization-controlled measurement has been considered to be a useful technique for selectively eliminating the diagonal peaks from the 2D spectrum.1-4 Sometimes, one can measure the anisotropy of cross-peak to determine the relative angle between two different transition dipoles, which can provide information on the 3D structure of target molecules such as peptides in solution.
