Spectral Properties of Monomeric Bacteriochlorophyll C in Nematic Liquid Crystal

Dudkowiak, Alina; Francke, Christof; Planner, A.; Cegielski, R.; Hanyż, I.; Amesz, J.; Fra̧ckowiak, D.

doi:10.1007/978-94-009-0173-5_49

Cited by 2 publications

(2 citation statements)

References 16 publications

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“…We finally note that when calculating the various spectra, we have taken the transition frequency ω 0 of a single BChl c molecule to agree with a wavelength of 675 nm, 50-53 while we used for the dipole squared of a single molecule µ 2 ≈ 20 Debye 2 . The latter value was obtained from the integrated extinction coefficient of monomeric solutions of BChl c 50,52,53 , using the expression from ref 51.…”

Section: Numerical Results and Discussionmentioning

confidence: 99%

Optical Properties of Helical Cylindrical Molecular Aggregates: The Homogeneous Limit

Didraga

Klugkist

Knoester³

2002

J. Phys. Chem. B

139

291

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Using a Frenkel exciton model, we study the optical absorption spectrum and linear and circular dichroism (CD) spectra of cylindrical molecular aggregates. We demonstrate that such aggregates can always be described as a stack of molecular rings with nearest-neighbor rings rotated relative to each other by a helical angle γ. For homogeneous aggregates, the cylindrical symmetry allows for a decomposition of the Hamiltonian into a set of effective one-dimensional Hamiltonians, which are characterized by a transverse wavenumber k 2 . The helical nature of the cylinder renders these Hamiltonians complex and noninversion symmetrical in general. Only the bands with k 2 ) 0 and k 2 ) (1 are dipole-allowed and yield contributions to the various linear spectra studied. The k 2 decomposition also allows for a convenient separation of the CD into ring and helical contributions, which in turn allows us to explain the strong sensitivity of this spectrum to various system parameters, such as the molecular orientations and the ratio of cylinder length and circumference. The latter is explicitly demonstrated by numerically studying the size dependence of the spectra for chlorosomes of green bacteria. The results suggest that the strong variation of the CD as reported experimentally may result from size variations. We also present analytical results valid for long cylinders. In this case, we find three superradiant states to be responsible for the complete linear optical response: one at total wave vector k ) 0 and the other two (degenerate) at wave vectors determined by the circumference and the helical angle γ.

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Section: Numerical Results and Discussionmentioning

confidence: 99%

Optical Properties of Helical Cylindrical Molecular Aggregates: The Homogeneous Limit

Didraga

Klugkist

Knoester³

2002

J. Phys. Chem. B

139

291

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“…The radius is given by R = 2.297 nm, while the length may extend to hundreds of nanometers. Finally, we use an average single-molecule transition frequency ω 0 that agrees with a wavelength of 660 nm, 45,46,47,48 while for the dipole squared of a single molecule we have used µ 2 ≈ 20 Debye 2 . The latter value was obtained from the integrated extinction coefficient of monomeric solutions of BChl c, 46,47,48 using the expression from Ref.…”

Section: Numerical Results For the Spectramentioning

confidence: 99%

Optical spectra and localization of excitons in inhomogeneous helical cylindrical aggregates

Didraga

Knoester

2004

The Journal of Chemical Physics

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We study the linear optical properties of helical cylindrical molecular aggregates accounting for the effects of static diagonal disorder. Absorption, linear dichroism, and circular dichroism spectra are presented, calculated using brute force numerical simulations and a modified version of the coherent potential approximation that accounts for finite size effects by using the appropriate open boundary conditions. Excellent agreement between both approaches is found. It is also shown that the inclusion of disorder results in a better agreement between calculated and measured spectra for the chlorosomes of green bacteria as compared to our previous report, where we restricted ourselves to homogeneous cylinders ͓Didraga, Klugkist, and Knoester, J. Phys. Chem. B 106, 11474 ͑2002͔͒. For the excitons that govern the optical response, we also investigate the disorder-induced localization properties. By analyzing an autocorrelation function of the exciton wave function, we find a strongly anisotropic localization behavior, closely following the properties of chiral wave functions which previously have been found for homogenoeus helical cylinders ͓Didraga and Knoester, J. Chem. Phys. 121, 946 ͑2004͔͒. It is shown that the circular dichroism spectrum may still show a strong dependence on the cylinder length, even when the exciton wave function is localized in a region small compared to the cylinder's size.

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Spectral Properties of Monomeric Bacteriochlorophyll C in Nematic Liquid Crystal

Cited by 2 publications

References 16 publications

Optical Properties of Helical Cylindrical Molecular Aggregates: The Homogeneous Limit

Optical Properties of Helical Cylindrical Molecular Aggregates: The Homogeneous Limit

Optical spectra and localization of excitons in inhomogeneous helical cylindrical aggregates

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