Two-photon absorption spectrum of oriented trans-polyacetylene

Halvorson, C.; Heeger, A.J.

doi:10.1016/0009-2614(93)90132-k

Cited by 25 publications

(5 citation statements)

References 16 publications

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“…Pariser−Parr−Pople quantum mechanical calculations have shown that a strong alternation in electron-transfer integrals along a polymer chain leads, except when there is strong electron correlation, to the lowest lying singlet excited state having a dipole-allowed fluorescent relaxation path to the ground state as confirmed by the absence of fluorescence of polyacetylene . In the case of PPV, the allowed 1 1 Bu state lies 0.5 eV lower than the 2 1 Ag state, which agrees with its high fluorescence yield.…”

Section: Electrooptical Fate Of An Excitation In Conjugated Materialssupporting

confidence: 54%

Organic-Based Electronics à la Carte

1999

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Francis Garnier was born in Marrakech in 1939, and received his education in physics and in chemistry at the University of Paris, where he obtained his Ph.D. in 1968. He is currently Research Director at CNRS and head of the Laboratoire des Mate ´riaux Mole ´culaires. His core research interests encompass the field of material science, including chemical synthesis, electrochemistry, spectroscopies, and photophysics and its interfaces with solid-state physics and biology.

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Section: Electrooptical Fate Of An Excitation In Conjugated Materialssupporting

confidence: 54%

Organic-Based Electronics à la Carte

1999

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“…In the bulk limit the 1 1 B − u and 2 1 A + g energies are ca. 0.8 eV higher than data from linear [20] and 2-photon [21] absorption and third harmonic generation [22] experiments on PA thin films. This implies that there are more substantial energy decreases due to solvation and aggregation (interchain hopping and eximer formation) effects.…”

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confidence: 60%

Electron-Lattice Relaxation, and Soliton Structures and Their Interactions in Polyenes

Bursill

Barford

1999

Phys. Rev. Lett.

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Density matrix renormalisation group calculations of a suitably parametrised model of long polyenes (polyacetylene oligomers), which incorporates both long range Coulomb interactions and adiabatic lattice relaxation, are presented. The 1 3 B + u and 2 1 A + g states are found to have a 2-soliton and 4-soliton form, respectively, both with large relaxation energies. The 1 1 B − u state forms an exciton-polaron and has a very small relaxation energy. The relaxed energy of the 2 1 A + g state lies below that of the 1 1 B − u state. The soliton/anti-soliton pairs are bound.Electronic interactions in polyenes and polyacetylene (PA) induce strong spin-density-wave correlations in the ground state, resulting in low energy spin-flip (or covalent) triplet ( 3 B + u ) excitations. These combine to form even-parity (dipole-forbidden) singlet ( 1 A + g ) excitations. Optical (dipole-allowed) transitions to the odd-parity singlet state ( 1 B − u ) are essentially ionic in character, resulting in charge transfer from one site to another. In the non-interacting limit the 1 3 B + u and 1 1 B − u states are degenerate, and the 2 1 A + g state always lies higher in energy. However, electron correlations can lead to a reversal of the energetic ordering of the 1 1 B − u and 2 1 A + g states. Electron-electron correlations in π conjugated systems, such as PA, are conveniently modelled by the one-band Pariser-Parr-Pople (P-P-P) model, which includes long range Coulomb interactions.Electron-phonon interactions in the non-interacting limit are described by the SSH model. In the adiabatic limit it predicts a wealth of non-linear excitations, including charged/spinless (S ± ) and neutral/spin 1/2 (S σ ) solitons. It is the inter-play of both electron-electron and electron-phonon interactions in PA which leads to an extremely rich variety of excitations. To describe these excitations we employ the density matrix renormalisation group (DMRG) [1] method to solve the P-P-P-SSH model, and utilise the Hellmann-Feynman (H-F) theorem to calculate the low-lying excited states and the lattice relaxation associated with them.Earlier work on the solitonic structure of the low-lying excitations include, a renormalisation group calculation of the Hubbard-SSH model of up to 16 sites [2]; a meanfield study of the Heisenberg-Peierls model [3]; an exact diagonalisation of a 12 site extended Hubbard-SSH model [4]; and a strong coupling and perturbation calculation of the Hubbard-SSH model [5]. The DMRG method has recently been used by and Yaron et al. [6] and Fano et al. [7] to solve the P-P-P model for linear and cyclic polyenes, respectively. Jeckelmann [8] studied the metal-insulator transition in doped PA by solving the extended Hubbard-SSH with the DMRG method. Likewise, Kuwabara et al.[9] used the DMRG method to study the relative stability of bipolarons using the same model.The P-P-P-SHH Hamiltonian is defined aswhere, t i = t 0 + ∆iis the bond order operator of the ith. bond. We use the Ohno function for the Coulomb interaction: V ij = U/ 1 + βr 2 i...

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“…In this case we expect D t ͞D s Ӎ ͑E 2,s ͞E 2,t ͒ 2 , where t and s refer to t-͑CH͒ x and s-͑CH͒ x , respectively. E 2 was respectively measured in these two polymers by two photon absorption (TPA) [21] and transient strain spectroscopy [22], and found to be E 2,t 1.1 eV and E 2,s 1.85 eV. Using these values in Eq.…”

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confidence: 99%

Dispersion of Resonant Raman Scattering inπ-Conjugated Polymers: Role of the Even Parity Excitons

et al. 1997

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Resonant Raman scattering dispersion of the most strongly coupled phonon frequencies with the excitation laser photon energy is measured in terms of a dispersion rate parameter D and quantified in a variety of p conjugated polymer films. D was found to be large in nonluminescent polymers and small in luminescent polymers. We show that D is determined by the dependence of the even parity excitons ͑A g ͒ on the polymer conjugation length, and this may serve as a useful spectroscopy for the 2A g exciton in nonluminescent polymers where it is otherwise optically inactive. [S0031-9007(97)03892-1]

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Two-photon absorption spectrum of oriented trans-polyacetylene

Cited by 25 publications

References 16 publications

Organic-Based Electronics à la Carte

Organic-Based Electronics à la Carte

Electron-Lattice Relaxation, and Soliton Structures and Their Interactions in Polyenes

Dispersion of Resonant Raman Scattering inπ-Conjugated Polymers: Role of the Even Parity Excitons

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