Vibronic models for nonlinear spectroscopy simulations.

It is already well established that the high-frequency intramolecular vibrations are responsible for many observed dynamic phenomena in linear and nonlinear electronic spectroscopy such as the spectral lineshape formation, the transition dipole moment, the lifetime borrowing, and vibrational and mixed coherence beats. All these implications together with the vibronic enhancement of the energy and charge transfer can be explained by the vibronic molecular exciton theory and are highly relevant for the description of the spectral dynamics in photosynthetic pigment-protein complexes. In this paper, a few critical points of the vibronic theory application to linear and nonlinear signals are discussed. Models, which differ in the selection and truncation of molecular basis, are compared by analyzing the energy spectrum and exciton-vibrational dynamics in the presence of the energetic disorder. The limits of the widely used one-particle approximation are defined.