Vibronische Kopplung und exzitonischer Anregungstransfer in molekularen Aggregaten
Final Report Abstract
In this project we have been concemed with the optical and energy transfer properties of Quantum Aggregates, loosely-coupled assemblies of objects displaying quantum behaviour and which largely retain their character on aggregation. The prime focus of attention throughout has been classes of large organic dye molecules but the basic theory has been generalized so as to be applicable to other aggregates, e.g. those of quantum dots, nano-partides, cold Rydberg atoms etc. Many such aggregates have great potential for technical application, in solar cells, in molecular electronics and other nano-devices. In the case of dye aggregates we have developed a simple approximation, the coherent exciton scattering (CES) approach which has had great success in explaining the dramatic spectral changes that accompany aggregation. In particular, after seventy years, we were able to explain the H band of pinacyonal dye, measured by Scheibe in München in 1938. Helical and cylindrical dye aggregates are unusual in that they form by spontaneous organization into these geometries, where the aggregates then exhibit optical activity, absent in the individual monomers. This has been explained in detail by generalising the CES method to circular dichroic spectra. Finally, the theory has been transformed to the time-dependent picture, allowing us to discuss the transport of electronic excitation along extended quantum structures in the presence of vibronic coupling both to intemal vibrations and those of the surrounding medium. This process of energy transport is also of interest to solar-cell development and of course in the important case of energy transfer in the photosynthetic unit.
Publications
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DPG-Tagung, Regensburg, 25.03.-30.03.2007, Regensburg 3. International Conference on Dynamical Processes in Excited States of Solids
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The Shape of the J-band of Pseudoisocyanine, A. Eisfeld and J. S. Briggs, Chem. Phys. Lett. 446, 354 (2007)
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Theory of the Absorption- and Circular Dichroism-spectra of helical molecular aggregates, A. Eisfeld, R. Kniprath, and J. S. Briggs, J. Chem. Phys. 126, 104904 (2007)
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Exchange Narrowing of the J-band of Molecular Dye Aggregates, P. B. Walczak, A. Eisfeld, and J. S. Briggs, J. Chem. Phys. 128, 044555 (2008)
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The 7th Intemational Conference on Excitonic Processes in Condensed Matter (EXCON'06), 26.-30.06.2006, Wake Forest, U.S.A.
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The Absorption Spectra of Quantum Aggregates interacting via Long-Range Forces, A. Eisfeld and J. S. Briggs, Phys. Rev. Lett. 96, 113003 (2006)
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The J- and H-bands of Dye Aggregate spectra: Analysis ofthe coherent exciton scattering (CES) approximation, J. Roden, A. Eisfeld, and J. S. Briggs, Chem. Phys. 352, 258 (2008)
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The J- and H-Bands of Organic Dye Aggregates, A. Eisfeld, J. S. Briggs, Chemical Physics 324, 376 (2006)
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Vibronic Energies and Spectra of Molecular Dimers, A. Eisfeld, L. Braun, W. T. Strunz, J. S. Briggs, J. Beck and V. Engel, J. Chem. Phys.122, 134103(2005)
