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1
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Relaxation of Excited Eu(III) Complexes in Cetyltrimethylammonium Bromide Micellar Solutions

100%
Sennoga C., Flint C.
Acta Physica Polonica A
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1996
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vol. 90
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issue 2
327-332
EN
The equilibria between pyridine-2,6-dicarboxylate and Eu(III) in H_{2}O or D_{2}O cetyltrimethylammonium bromide micellar solutions at room temperature have been made as a function of the ligand concentration and pH by excitation spectroscopy and emission decay measurements. Formation of the tris-complex is complete at [Eu^{3+}]:[pdc^{2-}] ≥ 1:4 at neutral to slightly alkaline conditions but is incomplete under acidic conditions. The ^{5}D_{0} lifetimes corresponding to the Eu(pdc)_{3}^{3-} anion is observed to increase on association of the complex with the micellar surface due to exclusion of the solvating molecules from the second co-ordination sphere. Energy transfer in the bulk solution requires the presence of binuclear mixed Eu^{3+} and Nd(pdc)_{3}^{3-} complexes or confinement of the Ln(pdc)_{3}^{3-}/Eu^{3+} on the micelle surface. Energy transfer from the Eu(pdc)_{3}^{3-} anion is inefficient in the bulk solution.
2
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Influence of Protein Vibrations on Electron Transfer

80%
Babincová M., Babinec P.
Acta Physica Polonica A
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1993
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vol. 84
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issue 2
365-367
EN
Using a double well model complemented with the third excited state it is shown that a new excited-state-induced protein vibration-mediated channel, with an electron transfer rate comparable to a standard tunneling rate may exist. This channel can become dominant at low temperatures.
3
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Energy Transfer in Peridinin-Chlorophyll-Protein-Metallic Nanoparticle Hybrid Nanostructure: Effect of Spatial Arrangement

80%
Schmidt M., Mackowski S.
Acta Physica Polonica A
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2012
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vol. 122
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issue 2
307-311
EN
We theoretically investigate dynamics of excitation in a hybrid nanostructure comprising a photosynthetic complex peridinin-chlorophyll-protein (PCP) coupled to a gold spherical nanoparticle. Our model includes the analytical description of radiative and non-radiative relaxation channels of the chlorophylls in PCP, as well as the change of energy transfer rate within the PCP due to the presence of metal scatterer. We show that by measuring the intensity of fluorescence from selectively excited chlorophyll molecules in the PCP complex, elementary geometric properties of the system can be deduced.
4
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The Light Harvesting Process in Purple Bacteria

80%
Krueger B., Scholes G., Yu J., Fleming G.
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vol. 95
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issue 1
63-83
EN
We present and review the results of fluorescence upconversion and photon echo experiments, and $ab initio$ calculations performed in our group within the last few years with respect to the light harvesting process in purple bacteria. Carotenoids transfer energy to bacteriochlorophyll (BChl) mainly via the carotenoid S_{2} → BChl Q_{x} pathway on a ~100 fs timescale. This transfer is reasonably reproduced by considering the Coulombic coupling calculated using the transition density cube method which is valid at all molecular separations. Carotenoids may also serve a role in mediating B800 → B850 energy transfer in LH2 by perturbing the transition density of the B850 as shown by ab initio calculations on a supermolecule of two B850 BChls, one carotenoid and one B800 BChl. Further calculations on dimers of B850 BChl estimate the intra- and interpolypeptide coupling to be 315 and 245 cm^{-1}, respectively. These interactions are dominated by Coulombic coupling, while the orbital overlap dependent coupling is ~20% of the total. Photon echo peak shift experiments (3PEPS) on LH1 and the B820 subunit are quantitatively simulated with identical parameters aside from an energy transfer time of 90 fs in LH1 and ∞ in B820, suggesting that excitation is delocalized over roughly two pigments in LH1. 3PEPS data taken at room and low temperature (34 K) on the B800-B820 suggest that static disorder is the dominant mechanism localizing excitation in LH1 and LH2. We suggest that the competition between the delocalizing effects of strong electronic coupling and the localizing effects of disorder and nuclear motion results in excitation in the B850 and B875 rings being localized on 2-4 pigments within approximately 60 fs.
5
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Theory of Translational Energy Relaxation in Binary Mixtures of Dilute Gases with Chemical Reaction

70%
Cukrowski A., Fritzsche S., Popielawski J.
Acta Physica Polonica A
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1992
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vol. 82
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issue 6
1005-1022
EN
A simple approach to the process of translational energy relaxation in dilute gases due to Dahler, Malkin, Shizgal and others is extended to the case of systems with chemical reaction. Fundamental quantities characterizing the relaxation processes such as the relaxation time and collision numbers during this time are computed for a number of molecular models of the chemical reaction (the Prigogine-Xhrouet model, the line-of-centers model, a modified line-of-centers model, and reverse versions of these models). Results of this analytical theory are compared with the results of numerical simulations of solutions of the appropriate Boltzmann equation with the use of the modified Nanbu-Babovsky method. This comparison leads to very good agreement between the analytical theory and numerical calculations. A marked influence of the chemical reaction on the translational relaxation in a dilute gas is another important conclusion of this paper.
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