Kinetic model of primary energy transfer and trapping in photosynthetic membranes

Abstract

The picosecond time-domain incoherent singlet excitation transfer and trapping kinetics in core antenna of photosynthetic bacteria are studied in case of low excitation intensities by numerical integration of the appropriate master equation in a wide temperature range of 4-300 K. The essential features of our two-dimensional-lattice model are as follows: Förster excitation transfer theory, spectral heterogeneity of both the light-harvesting antenna and the reaction center, treatment of temperature effects through temperature dependence of spectral bands, inclusion of inner structure of the trap, and transition dipole moment orientation. The fluorescence kinetics is analyzed in terms of distributions of various kinetic components, and the influence of different inhomogeneities (orientational, spectral) is studied.A reasonably good agreement between theoretical and experimental fluorescence decay kinetics for purple photosynthetic bacterium Rhodospirillum rubrum is achieved at high temperatures by assuming relatively large antenna spectral inhomogeneity: 20 nm at the whole bandwidth of 40 nm. The mean residence time in the antenna lattice site (it is assumed to be the aggregate of four bacteriochlorophyll a molecules bound to proteins) is estimated to be approximately 12 ps. At 4 K only qualitative agreement between model and experiment is gained. The failure of quantitative fitting is perhaps due to the lack of knowledge about the real structure of antenna or local heating and cooling effects not taken into account.

Exciton–vibrational coupling in the dynamics and spectroscopy of Frenkel excitons in molecular aggregates

“…[67,98,107]. While Förster transfer occurs via incoherent excitation hopping between pigment molecules [169], delocalized exciton dynamics is better described as a relaxation process within an exciton manifold (for an application to the LH2 complex, see Ref. [111]).…”

“…(170) and the definitions ofḡ 1/2 (t) in Eq. (169), one obviously finds the initial conditions asρ 0,0 (0) = ρ(0) andρ m,n (0) = 0 (m = 0 or n = 0). The extension to the case of N terms in the expansion of the correlation function, i.e.…”

Ultrafast photoinduced dynamics in quantum dot-based systems for light harvesting

“…In FRET, the point dipole interaction is typically used for calculating the transfer rate [83]. This approximation is valid if the separation between excitation donor and acceptor is significantly larger than their sizes.…”

Conformational disorder and energy migration in MEH-PPV with partially broken conjugation

“…Calculating the Coulomb interaction between the corresponding transition densities 28 results in still more exact values of the Förster transfer rate, but needs much more effort. 29 In the following we use the method outlined by Pullerits and Freiberg, 30 which uses a Pauli master equation to describe the energy migration. In order to use the Pauli master equation the correlation time of the nuclear bath must be much shorter than the time scale of the site-to-site electronic jump process.…”