Optical absorption from polarons in a model of polyacetylene

Fesser, K.; Bishop, A. R.; Campbell, D. K.

doi:10.1103/physrevb.27.4804

Cited by 555 publications

(210 citation statements)

References 31 publications

Supporting

Mentioning

194

Contrasting

Unclassified

Order By: Relevance

“…Hamiltonian obtained is the same as that considered by Fesser, Bishop and Campbell [7] as a model for cis − (CH) x .…”

Section: The Model Hamiltonianmentioning

confidence: 74%

“…The polaron solutions corresponding to the global (stable) minimum, had already been studied in references( [5,7,10,15]), these solutions reach ∆ o+ asymptotically when |x| → ∞.…”

Section: Polaron Solutionsmentioning

confidence: 99%

“…Borrowing from the known results for the degenerate case [11] and for the stable minimum [5,7,10](cis) we propose the static polaron solution as…”

Section: Polaron Solutionsmentioning

confidence: 99%

“…The properties of the polaron excitations of the stable (cis) phase were thoroughly studied within the continuum electron-phonon model and show the property of "confinement", that is their energy grows linearly with the spatial size of the lattice distortion [5,7,8,10]. Because of the lack of degeneracy, there are no stable topological soliton excitations in this case.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Polarons as nucleation droplets in nondegenerate polymers

1994

View full text Add to dashboard Cite

We present a study of the nucleation mechanism that allows the decay of the metastable phase (trans-cisoid) to the stable phase (cis-transoid) in quasi one-dimensional non-degenerate polymers within the continuum electronphonon model. The electron-phonon configurations that lead to the decay, i.e. the critical droplets (or transition state), are identified as polarons of the metastable phase. We obtain an estimate for the decay rate via thermal activation within a range of parameters consistent with experimental values for the gap of the cis-configuration. It is pointed out that, upon doping, the activation barriers of the excited states are quite smaller and the decay rate is greatly enhanced. Typical activation energies for electron or hole polarons are ≈ 0.1 eV and the typical size for a critical droplet (polaron) is about 1 20Å. Decay via quantum nucleation is also studied and it is found that the crossover temperature between quantum nucleation and thermal activation is of order T c ≤ 40 o K. Metastable configurations of non-degenerate polymers may provide examples for mesoscopic quantum tunneling.pacs No:71.10.+x;71.20.Hk;64.60.My

show abstract

“…Hamiltonian obtained is the same as that considered by Fesser, Bishop and Campbell [7] as a model for cis − (CH) x .…”

Section: The Model Hamiltonianmentioning

confidence: 74%

“…The polaron solutions corresponding to the global (stable) minimum, had already been studied in references( [5,7,10,15]), these solutions reach ∆ o+ asymptotically when |x| → ∞.…”

Section: Polaron Solutionsmentioning

confidence: 99%

“…Borrowing from the known results for the degenerate case [11] and for the stable minimum [5,7,10](cis) we propose the static polaron solution as…”

Section: Polaron Solutionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Polarons as nucleation droplets in nondegenerate polymers

1994

View full text Add to dashboard Cite

show abstract

“…This is in contrast to the results with tight binding methods. 16,90 The effect of the counterions was investigated for 9P-Cl 3 , 11P-Cl 3 , 13P-Cl 3 , and 19P-Cl 3 . Data are included in Table 2.…”

Section: Resultsmentioning

confidence: 99%

Theoretical Modeling of the Doping Process in Polypyrrole by Calculating UV/Vis Absorption Spectra of Neutral and Charged Oligomers

Okur

Salzner

2008

J. Phys. Chem. A

View full text Add to dashboard Cite

Changes in absorption spectra during doping of oligopyrroles were investigated with time-dependent density functional theory on optimized structures of neutral, singly, and doubly charged pyrrole oligomers with up to 24 rings. In the absence of counterions, defects are delocalized. Counterions induce localization. For dications two polarons on the same chain are preferred over a bipolaron. Intragap absorptions arise in charged species, no matter whether defects are localized or delocalized. Cations and dications give rise to two sub-band transitions. The cation peaks have lower energies than those of dications. The first excitations of cations have lower oscillator strengths than the second; for dications the second peak is weaker than the first. For very long oligomers, the second sub-band absorption vanishes and a third one appears at higher energy. The behavior of pyrrole oligomers is analogous to that of thiophene oligomers. Theoretical UV spectra for cations and dications of short oligomers (six to eight rings) match experimental spectra of polypyrrole at low and at high doping levels, respectively. The error in the theoretical calculations is about 0.4 eV, slightly larger than for thiophene oligomers at the same level of theory.

show abstract

Redox States of Long Oligothiophenes: Two Polarons on a Single Chain

Haare

Havinga

Dongen

et al. 1998

Chemistry A European J

261

309

View full text Add to dashboard Cite

A detailed investigation is presented of the redox states of three oligothiophenes (nT) with 6, 9, and 12 thiophene units. While open-shell radical cations (polarons) and closed-shell dications (bipolarons) are usually invoked as the primary redox species in these systems, we have obtained evidence that the dication of the longest oligothiophene (12T) has an electronic structure with two individual polarons. The redox states of 6T, 9T, and 12T have been fully characterized using UV/visible/near-IR and ESR spectroscopy in combination with electrospray mass spectrometry. For 6T and 9T, singleelectron oxidation in dichloromethane produces the corresponding radical cations, which form spinless p dimers at lower temperatures. A second oxidation step forms dications which possess a bipolaronic electronic structure. However, the redox behavior of the longest oligothiophene, 12T, is entirely different. Radical cations of 12T disproportionate into neutral oligomers and dications, except at the lowest oxidation levels. The spectral data for doubly oxidized 12T are incompatible with those expected for a bipolaronic structure but are consistent with the formation of two individual polarons on a single chain; this interpretation is also supported by the results from correlated quantum chemical calculations.

show abstract

Optical absorption from polarons in a model of polyacetylene

Cited by 555 publications

References 31 publications

Polarons as nucleation droplets in nondegenerate polymers

Polarons as nucleation droplets in nondegenerate polymers

Theoretical Modeling of the Doping Process in Polypyrrole by Calculating UV/Vis Absorption Spectra of Neutral and Charged Oligomers

Redox States of Long Oligothiophenes: Two Polarons on a Single Chain

Contact Info

Product

Resources

About