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1	Frenkel and Charge-Transfer Excitons in Quasi-One-Dimensional Molecular Crystals with Strong Intermolecular Orbital Overlap / Frenkel und Charge-Transfer Exzitonen in Quasi-Eindimensionalen Molekülkristallen mit starker intermolekularer Orbitalüberlappung Hoffmann, Michael 04 December 2000 (has links) (PDF) We present a theoretical and experimental study on the lowest electronically excited states in quasi-one-dimensional molecular crystals. The specific calculations and the experiments are performed for the model compounds MePTCDI (N-N'-dimethylperylene-3,4:9,10-dicarboximide) and TCDA(3,4:9,10-perylenetetracarboxylic dianhydride). The intermolecular interactions between nearest neighbors are quantum chemically analyzed on the basis of semi-empirical (ZINDO/S) Hartree-Fock calculations and a singly excited configuration interaction scheme. Supermolecular dimer states are projected onto a basis set of localized excitations. The nature of the lowest states is then completely explained as a superposition of molecular and low lying charge-transfer excitations. The CT excitations show a significant intrinsic transition dipole, which is oriented approximately parallel to the molecular planes and has a large component along the molecular M-axis. The exciton states in the one-dimensional stacks are described by a model Hamiltonian that includes interactions between three vibronic levels of the lowest molecular excitation and nearest-neighbor CT excitations. The three-dimensional crystal structure is considered by Frenkel exciton transfer between arbitrary molecules. This model is compared to polarized absorption spectra. With a small set of parameters, we can describe the key features of the absorption spectra, the polarization behavior, and the Davydov splitting. The variation of the polarization ratio for the various exciton states is analyzed as a direct qualitative proof for the mixing between Frenkel and charge-transfer excitons. 3 4:9 10-Perylentetracarbonsäuredianhydrid Charge-Transfer Exzitonen Dünne Schichten Frenkel Exzitonen MePTCDI N N'-Dimethylperylen-3 4:9 10-bis-dicarboximid Organische Kristalle PTCDA Polarisierte Absorption 3 4:9 10-perylenetetracarboxylic dianhydride Frenkel excitons MePTCDI N-N'-dimethylperylene-3 4:9 10-dicarboximide PTCDA charge-transfer excitons organic crystals polarized absorption thin films ddc:29 rvk:UP 3710 Absorptionsspektrum Exziton Kristallstruktur Ladungstransfer Molekülkristall Organischer Kristall Perylentetracarbonsäurederivate

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Frenkel and Charge-Transfer Excitons in Quasi-One-Dimensional Molecular Crystals with Strong Intermolecular Orbital Overlap / Frenkel und Charge-Transfer Exzitonen in Quasi-Eindimensionalen Molekülkristallen mit starker intermolekularer Orbitalüberlappung