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|Type:||Artigo de periódico|
|Title:||Band To Correlated Crossover In Alternating Hubbard And Pariser-parr-pople Chains: Nature Of The Lowest Singlet Excitation Of Conjugated Polymers|
|Abstract:||The evolution with increasing Coulomb correlations of a semiconductor to a magnetic insulator is related to an excited-state crossover in π-electron models for conjugated polymers. We associate strong fluorescence with a lowest singlet excitation S1 that is dipole allowed, on the band side, while S1 becomes two-photon allowed on the correlated side. S1/S2 crossovers in Hubbard, Pariser-Parr-Pople, or other chains with electron-hole symmetry and alternating transfer integrals t(1±δ) are based on exact results at δ=0 and 1, on molecular exciton theory at large δ, and on oligomer calculations up to twelve sites. © 1993 The American Physical Society.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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