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M. Hoffmann, Z.G. Soos, and K. Leo Absorption spectra and band structure of mixed Frenkel-charge-transfer vibronic states in one-dimensional molecular crystals, Nonlinear Optics 29 (2002) 227-237. | |
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| Abstract | |
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We discuss the excited state structure of a one-dimensional molecular
crystal. As in the Holstein model, we consider one Frenkel exciton
with nearest-neighbor hopping and linear coupling to one internal
vibration. Additionally, we include charge-transfer (CT) excitons that
couple to the same vibrational mode and mix with the Frenkel exciton.
The excited states of this model Hamiltonian are investigated by
numerical diagonalization. For this, we represent the Hamiltonian in a
displaced oscillator (Lang-Firsov) basis and use a problem-adapted
truncation scheme for the phonon basis. Thus, the complete optical
spectrum becomes accessible for weak up to intermediate electronic
coupling. As an example, we discuss the exciton structure of the
quasi-one-dimensional molecular crystals of PTCDA
(3,4,9,10-perylenetetracarboxylic dianhydride) and MePTCDI
(N-N'-dimethylperylene-3,4,9,10-dicarboximide). The experimental
linear absorption spectra can be well described by the k=0 states
using appropriate parameter sets. We present the resulting band
structure and compare the k=pi states with emission spectra.
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| pdf file of manuscript version | |
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homepage M. Hoffmann | |
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| last updated: M. Hoffmann, Dec 2007 |