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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 24: Poster: Organic Semiconductors

CPP 24.23: Poster

Mittwoch, 28. März 2012, 11:00–13:00, Poster A

Vibronic spectra of Frenkel excitons in a 2-dimensional polyacene lattice — •Peter Reineker¹, Ivan J. Lalov^{1, 2}, and Thomas Hartmann¹ — ¹Institute for Theoretical Physics, Ulm University, 89069 Uln, Germany — ²Faculty of Physics, Sofia University, Sofia 1164, Bulgaria

The vibronic spectra of Frenkel excitons (FEs) in a 2-dimensional lattice which models the (ab)-plane of polyacenes have been studied. The linear optical susceptibilities of the 2-dimensional crystal have been calculated using the Green functions method and the vibronic approach for the spectral ranges of FEs and their vibronic replicas. In the simulations of the vibronic spectra we use the excitonic and vibrational parameters of the crystals anthracene, tetracene and pentacene and obtain the linear absorption spectra in the excitonic and vibronic regions (FE plus one or several intramolecular vibrational quanta). The linear FE-phonon coupling is strong enough to create a bound or quasi-bound state of FE and one phonon, but it is not sufficient to bind the FE and more than one phonon. A hypothetical quadratic FE-phonon coupling makes the bound FE-phonon states more pronounced in the vibronic spectra. The strong transfer of the FE between two sublattices of the polyacene crystals widens the vibronic absorption lines.