Excitation Dynamics in Molecular Solids

Francis, Anthony; Kopelman, Raoul

doi:10.1007/3540167099_7

Cited by 9 publications

(3 citation statements)

References 128 publications

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“…For a triplet state, the distance d at which the energy-transfer rate is equal to the unimolecular decay rate is typically (3-5) X where Rm is the next neighbor distance (5 Á for naphthalene) in neat crystals. 41 The intermolecular distance is large (14 Á) in stoichiometric naphthalene choleic acid; therefore the number of sites visited by a donor excitation is small. Theories of single-step transfer and multistep energy transfer were used to fit the experimental data, and singlestep transfer provides the best fit.…”

Section: Discussionmentioning

confidence: 99%

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Triplet Excitation Energy Transfer in Naphthalenecholeic Acid Crystals

Kook¹,

Hanson²

1994

J. Phys. Chem.

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Investigation of triplet excitation energy dynamics in naphthalenecholeic acid crystals and isotopically mixed naphthalenecholeic acid crystals are described. Phosphorescence, sensitized phosphorescence of @-methylnaphthalene trap, and phosphorescence decay are observed at 16 and 4.2 K to characterize the energy-transfer dynamics. In neat stoichiometric crystals (33 mol % CloHa), the phosphorescence decays by unimolecular processes with a lifetime (2.7 f 0.1 s) characteristic of naphthalene. This exponential decay and the absence of delayed fluorescence indicate that exciton annihilation and impurity trapping do not occur in this system under the experimental conditions. In the isotopically mixed crystals, unimolecular decay dominates at low concentrations of CloHs ( 5 mol %, 28 mol % CloDg). At higher concentrations of CloHs, energy transfer to @-methylnaphthalene traps occurs at early times (1300 ms) after excitation until the exciton density is too low relative to the trap density for transfer. At long times then, unimolecular processes again dominate. At a C10H8 concentration of 20 mol %, the energy-transfer rate in isotopically mixed naphthalene crystals is 35 times larger than in the naphthalenecholeic acid system. From agreement between theory and the experimental data, it appears that a one-dimensional exchange interaction topology is consistent with triplet excitation energy transfer in this system.

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Section: Discussionmentioning

confidence: 99%

“…A for naphthalene) in neat crystals 41. The intermolecular distance is large (14 A) in stoichiometric naphthalene choleic acid; therefore the number of sites visited by a donor excitation is small.…”

mentioning

confidence: 99%

Triplet Excitation Energy Transfer in Naphthalenecholeic Acid Crystals

Kook¹,

Hanson²

1994

J. Phys. Chem.

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“…Since this mechanism depends crucially on the time, it has been called "dynamic percolation". 6 It should be mentioned that it is assumed throughout this work, as is commonly done in studies of isotopically mixed (proto in deutero) organic crystals, that the isotopic impurities enter the lattice randomly and substitutionally, since the host and trap are nearly chemically identical. Thus there are no inhomogeneous domains of protonated or deuterated species; whatever connections exist between traps are assumed to arise stochastically because of the random placement of traps near each other.…”

Section: Introductionmentioning

confidence: 99%

High Pressure Studies of Critical Concentration Triplet Energy Transfer in Naphthalene: Percolation or Anderson Delocalization?

Brenner

Variano

1989

Molecular Crystals and Liquid Crystals Incorporating Nonlinear

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Previous work has shown that ternary mixed crystals of naphthalene-h, (N-h) and betamethylnaphthalene (BMN) guests in a naphthalene-d, (N-d) host exhibit a critical concentration effect in which the phosphorescence intensity of BMN, which is present in very small concentration, rises sharply as the concentration of N-h traps passes through 13%. In the present investigation, high pressure is applied to test the validity of theoretical models for this critical concentration effect, and it is shown that at 4 kbar, the apparent critical concentration is lowered from 13% to 11%. High pressure also enhances supertrap capture and exciton fusion rates, as determined from phosphorescence decay measurements. It is tentatively concluded that the observed lowering of the critical concentration is consistent with a diffusive, dynamic percolation model, if one allows for reasonable increases in the exchange interaction p and the supertrap capture efficiency with pressure. The applicability of an Anderson-Mott description is not excluded by our results, but is considered unlikely on the basis of probable substantial increases in inhomogeneous broadening under pressure.

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Excitonic effects in the light‐harvesting Chl a/b–protein complex of higher plants

Voigt

Renger

Schödel

et al. 1996

Physica Status Solidi (b)

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Dedicated to Professor Dr. K. W. BOER on the occasion of his 70th birthday Exciton states and their coupling to long-wavelength protein vibrations are investigated both, experimentally and theoretically, in Chl a/b pigment-protein complexes acting as light-harvesting antennae in higher plants. It is shown that the 12 chlorophyll molecules located within the involved protein-monomers form extended exciton states and act cooperatively in the light absorption process. Besides one-exciton excitations also two-exciton excitations are demonstrated at higher photon densities incident on the monomer clusters resulting in nonlinear transmission and emission effects. The distribution of excitons over the exciton energy levels follows a Bolt,zmann law as shown by emission and nonlinear transmission experiments. The exciton-vibration coupling is weak as indicated by a resonance-like zero-phonon emission line which shows a strong reabsorption. Conclusions are drawn about the structure-function relationship of this antenna type. Interesting similarities between the biological structure investigated and semiconductors or semiconductor structures are discussed. respect t o the higher plants the light-harvesting Chl a/b complex acting as the external antenna of photosystem I1 (and therefore called LHC-11) is the most important antenna complex. It contains about half of the chlorophyll and half of the protein of the thylakoids of higher plants [l]. Therefore, this complex is very well appropriate for investigating the structure-function relationship of photosynthetic antennae.The main difference between inorganic or organic and bioorganic molecular structures consists in the fact that the hioorganic structures, as mentioned above, are selected during the evolution t o perform a special function, and only this function, with a high ') Invalidenstr. 110,

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Excitation Dynamics in Molecular Solids

Cited by 9 publications

References 128 publications

Triplet Excitation Energy Transfer in Naphthalenecholeic Acid Crystals

Triplet Excitation Energy Transfer in Naphthalenecholeic Acid Crystals

High Pressure Studies of Critical Concentration Triplet Energy Transfer in Naphthalene: Percolation or Anderson Delocalization?

Excitonic effects in the light‐harvesting Chl a/b–protein complex of higher plants

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