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[en] The coupled exciton–vibrational dynamics of a seven site Frenkel exciton model of the Fenna–Matthews–Olson (FMO) complex is investigated using a Quantum Master Equation approach. Thereby, one vibrational mode per monomer is treated explicitly as being part of the relevant system. Emphasis is put on the comparison of this model with that of a purely excitonic relevant system. Further, the effects of two different approximations to the exciton–vibrational basis are investigated, namely the one- and two-particle description. Analysis of the vibronic and vibrational density matrix in the site basis points to the importance of on- and inter-site coherences for the exciton transfer. Here, one- and two-particle approximations give rise to qualitatively different results.
[en] The fluorescence emission spectrum of single peripheral light-harvesting (LH2) complexes of the photosynthetic purple bacterium Rhodopseudomonas acidophila exhibits remarkable dynamics on a time scale of several minutes. Often the spectral properties are quasi-stable; sometimes large spectral jumps to the blue or to the red are observed. To explain the dynamics, every pigment is proposed to be in two conformational substates with different excitation energies, which originate from the conformational state of the protein as a result of pigment-protein interaction. Due to the excitonic coupling in the ring of 18 pigments, the two-state assumption generates a substantial amount of distinct spectroscopic states, which reflect part of the inhomogeneous distributed spectral properties of LH2. To describe the observed dynamics, spontaneous and light-induced transitions are introduced between the two states. For each 'realization of the disorder', the spectral properties are calculated using a disordered exciton model combined with the modified Redfield theory to obtain realistic spectral line shapes. The single-molecule fluorescence peak (FLP) distribution, the distribution dependence on the excitation intensity, and the FLP time traces are well described within the framework of this model
[en] Surface localization of the initial target-projectile interaction has been investigated for incident protons and neutrons at bombarding energies of 14--100 MeV within the framework of the exciton preequilibrium model. Incident neutrons, at least at energies up to around 30 MeV, show a greater amount of surface peaking than do incident protons as judged by the effective well depth available to the hole degree of freedom created. With this difference included, exciton model calculations can describe the energy spectra in all four (N,N) reaction channels with a consistent set of model input. To aid in this study, the excitation of strong spectroscopic collective states was included in the calculations. The addition of giant resonance state excitation has a small but helpful effect. There is a need for additional data, especially for incident neutrons above 26 MeV
[en] Nearly every technical information is chased in the world. All of them are reviewed and analyzed. Some of them are chosen to study further more to review every related documents. And a probable suggestion about the excitonic process in deuteron absorbed condensed matter is proposed a way to cold fusion. 8 refs. (Author)
[en] Excitons in carbon nanotubes may be modeled by two oppositely charged particles living on the surface of a cylinder. We derive three one-dimensional effective Hamiltonians which become exact as the radius of the cylinder vanishes. Two of them are solvable. (author)
[en] Paper deals with dynamics of a light field in a composite medium consisting of the Bragg unidimensional lattice with periodically placed resonance medium composed of extended molecules. J-aggregates of colours and conjoint polymers are considered as examples of a molecular medium. One investigates into adiabatic and nonadiabatic modes of dynamics of acoustic waves formed within the system under effect of electromagnetic field. One studied the effect of exciton-phonon-photon interactions on band structure and the conditions for formation of autolocalized excitations for various time scales. Paper describes a new mechanism to control the forbidden band parameters under the bistable conditions. One studied some aspects of the effect of electromagnetic field inhomogeneity in a medium on formation of acoustic waves in molecules and on autolocalization of excitons
[ru]Изучается динамика светового поля в композитной среде, состоящей из одномерной брэгговской решетки с периодически размещенной резонансной средой, состоящей из протяженных молекул. В качестве примеров молекулярной среды рассматриваются J-агрегаты красителей и сопряженные полимеры. Изучаются адиабатический и неадиабатический режимы динамики акустических волн, формирующихся в системе под действием электромагнитного поля. Изучено влияние экситон-фононного и экситон-фонон-фотонного взаимодействия на зонную структуру и условия формирования самолокализованных возбуждений для разных временных масштабов. Описан новый механизм управления параметрами запрещенной зоны в бистабильном режиме. Изучены некоторые аспекты влияния неоднородности электромагнитного поля в среде на формирование акустических волн в молекулах и самолокализацию экситонов
[en] The correspondence of the random walks and Markovian master equations to the two-dimensional problems of nuclear physics (namely the nucleon transfer in heavy-ion reactions and the two-component exciton model) is briefly sketched. The preference of the mathematical description for the real calculations should be connected to the physical conditions of the experiment. (author). 6 refs
[en] A microscopic theory of the exciton annihilation based on the superposition approximation for a three-particle density matrix is proposed. A new effect of the enhancement of luminescence quenching is predicted for excitons with the dispersion law close to one- or two-dimensional. (orig.)
[en] Quantum dynamical and electronic structure calculations are combined to investigate the mechanism of exciton migration in an oligothiophene HJ aggregate, i.e., a combination of oligomer chains (J-type aggregates) and stacked aggregates of such chains (H-type aggregates). To this end, a Frenkel exciton model is parametrized by a recently introduced procedure [Binder et al., J. Chem. Phys. 141, 014101 (2014)] which uses oligomer excited-state calculations to perform an exact, point-wise mapping of coupled potential energy surfaces to an effective Frenkel model. Based upon this parametrization, the Multi-Layer Multi-Configuration Time-Dependent Hartree (ML-MCTDH) method is employed to investigate ultrafast dynamics of exciton transfer in a small, asymmetric HJ aggregate model composed of 30 sites and 30 active modes. For a partially delocalized initial condition, it is shown that a torsional defect confines the trapped initial exciton, and planarization induces an ultrafast resonant transition between an HJ-aggregated segment and a covalently bound “dangling chain” end. This model is a minimal realization of experimentally investigated mixed systems exhibiting ultrafast exciton transfer between aggregated, highly planarized chains and neighboring disordered segments.