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|Type:||Artigo de periódico|
|Title:||One- And Two-photon Excitations Of Polythiophene: Role Of Nonconjugated Heteroatoms|
|Abstract:||We model the one- and two-photon excitations of polythiophene (PT) in terms of interacting π-electrons and a charge-density-wave (CDW) ground state due to S atoms. The Pariser-Parr-Pople (PPP) model for π-electrons is modified for a CDW ground state, with all additional Coulomb interactions leading to a site-energy difference of 2ε between the α and β carbons along the PT backbone. The polyene (ε = 0) ordering of the one- and two-photon excitations is reversed in nT oligomers with increasing ε and standard hydrocarbon parameters, with ε = 1.8 eV obtained from 2T and 3T data. The magnitude of tε is consistent with atomic charges obtained semiempirically and rationalizes two-photon PT spectra and fluorescence, which indicate S1 to be one-photon allowed. Polaron and bipolaren excitations of 2T and 3T are obtained exactly within the PPP model at ε = 0 and 1.8 eV for the ground-state geometry and compared to experiment. In-gap excitations of anions and cations differ significantly at ε = 1.8 eV upon lifting electron-hole symmetry. © 1994 American Chemical Society.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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