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Photosynth Res (2014) 121:95106 DOI 10.1007/s11120-014-0002-z
REGULAR PAPER
Vibronic models for nonlinear spectroscopy simulations
Egl_
e Bainskait_
e Vytautas Butkus
Darius Abramavicius Leonas Valkunas
Received: 16 December 2013 / Accepted: 27 March 2014 / Published online: 17 April 2014 Springer Science+Business Media Dordrecht 2014
Abstract 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 pigmentprotein 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 dened.
Introduction
Molecular (Frenkel) exciton theory is the cornerstone for theoretical description of electronic excitation behavior in molecular systems (Davydov 1962; Amerongen et al. 2000).
Various spectroscopic phenomena, for instance, motional narrowing in J-aggregates (Knapp 1984; Malyshev and Domnguez-Adame 1999), band formation of the absorption spectra and excitation dynamics in solids, and pigment protein complexes (Cho et al. 2005; Milota et al. 2009) are usually understood in terms of the exciton concept. Other phenomena, such as charge separation or vibrational/vibronic dynamics (Fulton and Gouterman 1964) are also explained within the frame of more elaborate treatments of the exciton theory. Along with the rapid development of multi-dimensional spectroscopy, Frenkel exciton is still employed as the basic concept in description of electronic excitations in photosynthetic pigmentprotein complexes (Scholes and Fleming 2011; Amerongen et al. 2000).
Coupling to vibrational degrees of freedom often is a dominating factor in the description of the exciton dynamics. This interaction usually called the vibronic interaction, introduces a distinct complexity into the (vibronic) exciton theory and, thus, can be accounted for in different ways. Low-frequency vibrations are usually represented as a continuum of bath modes and are characterized by the spectral...