Theory of Molecular Excitons

Davydov, A. S.

doi:10.1007/978-1-4899-5169-4

Cited by 1,096 publications

(791 citation statements)

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“…As is appropriate for molecular systems, we will use the Frenkel exciton model to describe the excited states [20]. Since we do not have detailed knowledge of the aggregate structure, we will take the simplest point of view and restrict ourselves to nearest neighbor excitation transfer interactions J between the molecules within each ring; interactions between rings are assumed to be sufficiently weak to be ignored.…”

Section: Theory Of Spectral Behavior Of Cylindrical Jaggregatesmentioning

confidence: 99%

Polarized absorption and anomalous temperature dependence of fluorescence depolarization in cylindrical J-aggregates

et al. 2002

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Polarized absorption and anomalous temperature dependence of fluorescence depolarization in cylindrical J-aggregates Spitz, C.; Knoester, J.; Ouart, A.; Daehne, S. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. AbstractWe study chiral J-aggregates of the amphiphilic dye 1A that are spontaneously and asymmetrically generated from achiral dye monomers. These aggregates occur in two types. One type possesses a threefold split J-absorption band and forms micrometer-sized superhelices. The other type has a twofold split J-absorption band and forms smaller nanoparticles. We show that the analysis of optical experiments with polarized light in terms of an exciton model yields strong indications that the smaller aggregates have a cylindrical structure as well; the lower exciton band is polarized along the cylinder axis, while the higher band is polarized perpendicular to it. Our analysis allows for an estimate of the number of molecules around the circumference of the cylinder. Fluorescence-polarization excitation spectra at room temperature confirm the cylinder model. At low temperature, these spectra reveal a surprising loss of fluorescence polarization upon excitation in the higher exciton band. Possible explanations for this observation are discussed. Ó

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Section: Theory Of Spectral Behavior Of Cylindrical Jaggregatesmentioning

confidence: 99%

Polarized absorption and anomalous temperature dependence of fluorescence depolarization in cylindrical J-aggregates

et al. 2002

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“…The latter can be modeled by coupling the exciton to a phonon bath. 32 When both static diagonal disorder and exciton-phonon interaction are taken into account, the total Hamiltonian becomes…”

Section: Model Considerationsmentioning

confidence: 99%

Exciton superradiance in aggregates: The effect of disorder, higher order exciton-phonon coupling and dimensionality

Potma

Wiersma

1998

The Journal of Chemical Physics

137

129

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In this paper a detailed theoretical analysis is presented of the temperature dependent radiative decay in aggregates of pseudoisocyanine ͑PIC͒. Our approach extends the original linear exciton-phonon coupling model used by Spano, Kuklinsky, and Mukamel ͓Phys. Rev. Lett. 65, 212 ͑1990͔͒ including static disorder and second order exciton-phonon interactions. It is shown that for a one-dimensional exciton model neither of these additional effects alone or in combination with linear electron-phonon coupling can explain the steep rise in radiative lifetime at 40 K observed in the J-aggregate of PIC. However, when the aggregate assembles into a two-dimensional bricklike structure its radiative dynamics can be simulated, with linear exciton-optical phonon coupling as the only source for exciton scattering. Exciton-phonon scattering transfers oscillator strength from the kϭ0 state to other band states and also generates a nonequilibrium population among the exciton states, which persists during the superradiant decay. These effects together explain the marked temperature dependence of the radiative lifetime of the PIC J aggregate. When disorder limits the coherence length at low temperatures to a few molecules, as seems the case in several light harvesting complexes, the exciton population can equilibrate on the time scale of the superradiance. This situation pertains to the strong collision limit of the master equation, where the radiative decay is insensitive to details of the electron-phonon coupling, but only senses change in the thermal population among the exciton states.

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“…This band is centered at the single-molecule transition frequency , and has a width of four times the interaction energy V between the molecules in the chain. The delocalized states are the well-known Frenkel excitons, 32 which are characterized by a single quantum number k. The N eigenstates of this band follow from Eqs. ͑2͒ and ͑5͒,…”

Section: ͑6͒mentioning

confidence: 99%

The dynamics of one-dimensional excitons in liquids

Bürgel

Wiersma

Duppen

1995

The Journal of Chemical Physics

214

198

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The properties of excitons in one-dimensional molecular aggregates, dissolved at room temperature in a liquid, were studied by means of femtosecond nonlinear optical experiments. Both the one-exciton band ͑i.e., Frenkel-excitons͒ and multiexciton bands contribute to the observed nonlinear optical response. The rapid motions in the liquid lead to ultrafast perturbations of the molecular energy levels. This localizes the excitons on limited sections of the chains of aggregated molecules. Ultrafast frequency-resolved pump-probe spectroscopy on the lowest two exciton bands was employed to determine the delocalization length of the optical excitations. The kinetics of the exciton populations was measured by ultrafast grating scattering experiments and time-resolved single photon counting. A model is described in which the multiexciton bands act as doorway states in the exciton-exciton annihilation process. These bands thereby determine the population decay of the Frenkel excitons at high excitation densities. Room temperature photon echo experiments show that stochastic perturbations of the exciton transition frequencies occur on two distinct time scales. In particular the slow components of the fluctuations are affected by motional narrowing, associated with the exciton delocalization length. It is therefore argued that the optical dephasing of excitons is directly related to the spatial extent of the excitation on the aggregate chain.

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Theory of Molecular Excitons

Cited by 1,096 publications

References 0 publications

Polarized absorption and anomalous temperature dependence of fluorescence depolarization in cylindrical J-aggregates

Polarized absorption and anomalous temperature dependence of fluorescence depolarization in cylindrical J-aggregates

Exciton superradiance in aggregates: The effect of disorder, higher order exciton-phonon coupling and dimensionality

The dynamics of one-dimensional excitons in liquids

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