On the contribution of the exciton–photon interaction to the exciton absorption line shape in the spatially inhomogeneous wave model: Application to the <i>a</i>-singlet exciton of naphthalene

Robinette, Susan Louise; Stevenson, Sylvia H.; Small, Gerald J.

doi:10.1063/1.436576

Cited by 20 publications

(3 citation statements)

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“…We propose that a significant contribution to this broadening is due to scattering of the B870 exciton level to the adjacent, higher energy E 1 levels due to absorption of bath (protein) phonons with energies equal to the B870−E 1 energy gap Δ E (energy disorder splits the E 1 degeneracy, vide supra). Such scattering has been thoroughly studied in organic crystals; see, for example, refs −21. By necessity, we simplify by using an average value for the energy gaps, Δ E , and express Γ h /2 (Figure ) as where n̄ is the previously defined phonon thermal occupation number with phonon energy equal to Δ E .…”

Section: Resultsmentioning

confidence: 99%

Exciton Level Structure and Energy Disorder of the B850 Ring of the LH2 Antenna Complex

et al. 1997

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Experimental and theoretical results are presented on the exciton level structure of the B850 ring of bacteriochlorophyll a molecules for the light-harvesting 2 (LH2) complex of Rhodopseudomonas acidophila (strain 10 050) and the effects of energy disorder (due to structural heterogeneity) on the level structure. The work is an outgrowth of the accompanying paper (Wu et al. J. Phys. Chem. B 1997, 101, 7641), which reports on the temperature and pressure dependencies of the LH2 absorption spectrum and the zero-phonon hole action spectrum of the lowest energy exciton level of the complex, B870, as well as the structural (nondenaturing) change of the complex near 150 K. The effects of energy disorder are analyzed using the theory of Wu and Small (Chem. Phys. 1997, 218, 225), which employs symmetry-adapted energy defect patterns. The analysis leads to a room temperature value of ∼100 cm-1 for the splitting between B870 and the adjacent, strongly allowed E1 level in the absence of disorder. Using the temperature-dependent data of Wu et al., we arrive at a theoretical estimate for this splitting at temperatures below ∼150 K of ∼150 cm-1, which is 50 cm-1 smaller than the “apparent” value of 200 cm-1 based on the 4.2 K B870 action spectrum. The 50 cm-1 difference is explained in terms of a distribution of values for the energy disorder parameter(s), which leads to a distribution of values for the oscillator strength of B870. Hole-burning data on the temperature dependence of B870's optical dynamics are presented and analyzed. Below ∼15 K the dynamics are dominated by two-level systems of the protein with an effective dephasing frequency that carries a T α dependence with α ≈ 1.3. At temperatures above ∼20 K the dephasing is strongly exponentially driven with an activation energy of ∼100−140 cm-1. A mechanism suggested for this dephasing is that it is due to upward scattering of the B870 level to the adjacent E1 level by one-phonon absorption. New satellite hole spectra for the LH2 complex (isolated and chromatophores) are presented that lead to the assignment of the weak high-energy tail absorption of the B800 and B850 absorption bands to B850 exciton levels of the B850 ring, which are either symmetry forbidden or predicted to be very weakly absorbing in the absence of energy disorder.

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Section: Resultsmentioning

confidence: 99%

Exciton Level Structure and Energy Disorder of the B850 Ring of the LH2 Antenna Complex

et al. 1997

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“…However, we note that the narrowest linewidths measured for this system, on carefully prepared samples. have been [62] about 0.3 cm-', and the extrapolated phonon-caused homogeneous licebroadening is an order of magnitude smaller [SO]. Thus, there appears to be good apreement between the lower Iimit to the first stnglet exciton coherence time derived from spectral linewidths and that derived here from the exciton percolation method [32] (see discussion).…”

Section: Percolation and Energy Transportmentioning

confidence: 76%

Dynamics of energy transport in ternary molecular solids. I. Naphthalene steady state fluorescence

Argyrakis

Kopelman

1981

Chemical Physics

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Energy transport experiments were conducted at liquid helium temperatures on ternary sin$e crystals (host/guest/ supertrap, i.e. C,oH,/C,oD,/beramethylnaphthaIene-d,,) at guest concentrations of SO-99% and very low (about 10-s) supertrap concentrations. The relative supertrap to guest steady-state fluorescence _gives a measure of the exciton percolation probability (migration to the supertrap). The onset of efficient transport is observed at about 85% C,,H,, compared to about 50% at higher supertrsp concentrations bearing out the kinetic nature of the transport (e.g. dynamic percolation). The wealth of data are iuell fitted by an effectively two-dimensional percolation formalism containing a single parameter cf "coherency", i.e. an exciton mean free path (in nearest neighbor lattice units), extrapolated to the pure crystal (naphtharene). Our result gives about IO' or more correlated hoppings (retaining directional memory) and is consistent with linewidth information and with time-resolved studies.

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“…Gerry introduced a theory of polariton relaxation to explain these important results (Robinette et al 1978;Stevenson et al 1981). Gerry also introduced some remarkable new methods for chemical carcinogenesis and laser bioanalysis that are based on the use of nonlinear optical processes to simplify complex spectra.…”

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confidence: 99%

Remembering Gerald J. Small (1941–2004), who tackled everything in life with an intense and enviable passion

Jankowiak

Seibert

2005

Photosynth Res

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On the contribution of the exciton–photon interaction to the exciton absorption line shape in the spatially inhomogeneous wave model: Application to the a-singlet exciton of naphthalene

Cited by 20 publications

References 8 publications

Exciton Level Structure and Energy Disorder of the B850 Ring of the LH2 Antenna Complex

Exciton Level Structure and Energy Disorder of the B850 Ring of the LH2 Antenna Complex

Dynamics of energy transport in ternary molecular solids. I. Naphthalene steady state fluorescence

Remembering Gerald J. Small (1941–2004), who tackled everything in life with an intense and enviable passion

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