Spectrum of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>χ</mml:mi></mml:mrow><mml:mrow><mml:mn /><mml:mo>(</mml:mo><mml:mn>3</mml:mn><mml:mo>)</mml:mo><mml:mn /></mml:mrow></mml:msup></mml:mrow></mml:math>(-3ω;ω,ω,ω) in polyacetylene: An application of free-electron laser in nonlinear optical spectroscopy

Fann, W.S.; Benson, Stephen; Madey, J. M. J.; Etemad, S.; Baker, Gregory L.; Kajzar, F.

doi:10.1103/physrevlett.62.1492

Cited by 236 publications

(69 citation statements)

References 14 publications

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“…1 On the other hand, the excited states energy levels are often measured in these polymers by cw optical techniques, including electroabsorption 2,3 and resonant Raman scattering, [4][5][6] and by two and three photon nonlinear optical spectroscopies. 7,8 In this paper we introduce a version of cw photomodulation action spectroscopy, which is capable of measuring the photogeneration dynamics of secondary photoexcitations without the need of ps transient optical techniques. This technique uses the excitation dependence ͑action spectrum͒ of various photoinduced absorption ͑PA͒ bands in the photomodulation spectrum, measured under conditions far from the steady state.…”

Section: Introductionmentioning

confidence: 99%

Photogeneration and recombination processes of neutral and charged excitations in films of a ladder-type poly(para-phenylene)

et al. 1999

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We introduce a version of the cw photomodulation technique, measured far from the steady state, for obtaining the quantum efficiency, , of long-lived photoexcitations in -conjugated polymers. We apply this technique to films of a ladder-type poly͑para-phenylene͒ ͓mLPPP͔ for studying the photogeneration action spectra, (E), and recombination kinetics of photogenerated neutral and charged excitations such as singlet and triplet excitons and charged polarons. Whereas the (E) spectrum for singlet excitons shows a step function increase at a photon energy, E, close to the optical gap (Ӎ2.6 eV), both triplet and polaron (E) spectra show, in addition, a monotonous rise at higher E. The rise for triplets is explained by singlet exciton fission into triplet pairs, and from a model fit we get the triplet exciton energy (Ӎ1.6 eV). For polarons this rise is modeled by an electron intersegment tunneling process. The electroabsorption spectrum is also measured and analyzed in terms of Stark shift of the lowest lying exciton, 1B u , and enhanced oscillator strength of the important mA g exciton. A consistent picture for the lowest excited state energy levels and optical transitions in the neutral ͑singlet and triplet͒ and charged manifolds is presented. From both the exciton binding energy of Ӎ0.6 eV and the singlet-triplet energy splitting of Ӎ1 eV, we conclude that the e-e interaction in mLPPP is relatively strong. Our results are in good agreement with recent ab initio band structure calculations for several -conjugated polymers. ͓S0163-1829͑99͒13531-8͔

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Section: Introductionmentioning

confidence: 99%

Photogeneration and recombination processes of neutral and charged excitations in films of a ladder-type poly(para-phenylene)

et al. 1999

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“…Kz, 72.20.Jv, 78.30.Jw, 78.66.Qn The photogeneration dynamics of singlet excitons and secondary photoexcitations, such as triplets and polarons, in p-conjugated polymers have been usually measured by picosecond transient spectroscopic techniques rather than cw spectroscopies, since their photogeneration processes usually occur in the subnanosecond time domain [1]. On the other hand, the excited states energy levels of these polymers are often measured by cw optical techniques including electroabsorption [2], resonant Raman scattering [3], and by two and three photon nonlinear optical spectroscopies [4]. In this Letter we employ a new version of the cw photomodulation (PM) spectroscopy technique, which is capable of measuring the photogeneration quantum efficiency, h, of long-lived secondary photoexcitations without the need of transient optical techniques.…”

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confidence: 99%

Photogeneration Action Spectroscopy of Neutral and Charged Excitations in Films of a Ladder-Type Poly(Para-Phenylene)

et al. 1999

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The photogeneration quantum efficiency action spectra of long-lived neutral and charged excitations in films of a ladder-type poly(para-phenylene) were measured. We found that both triplet and polaron action spectra show, in addition to a step function increase at the optical gap, a monotonic rise at higher energies. For triplets this rise is explained by singlet exciton fission into triplet pairs from which the triplet exciton energy in the gap was obtained; this energy was also confirmed by measuring the weak phosphorescence band. For polarons the photogeneration increase at high energies is modeled by a novel hot electron interchain tunneling process. [S0031-9007(99)08980-2] PACS numbers: 78.55. Kz, 72.20.Jv, 78.30.Jw, 78.66.Qn The photogeneration dynamics of singlet excitons and secondary photoexcitations, such as triplets and polarons, in p-conjugated polymers have been usually measured by picosecond transient spectroscopic techniques rather than cw spectroscopies, since their photogeneration processes usually occur in the subnanosecond time domain [1]. On the other hand, the excited states energy levels of these polymers are often measured by cw optical techniques including electroabsorption [2], resonant Raman scattering [3], and by two and three photon nonlinear optical spectroscopies [4]. In this Letter we employ a new version of the cw photomodulation (PM) spectroscopy technique, which is capable of measuring the photogeneration quantum efficiency, h, of long-lived secondary photoexcitations without the need of transient optical techniques. We show that when the PM signal is measured under conditions far from the steady state, then it directly correlates with h; therefore the PM action spectrum (PMAS) measured under these conditions gives the dependence of h on the excitation photon energy, E, i.e., h͑E͒.We have used the PMAS technique to obtain h͑E͒ of singlet and triplet excitons and polarons, respectively, in films of methyl-substituted ladder-type poly(paraphenylene) (mLPPP) [5] shown in Fig. 1, inset. mLPPP is an attractive p-conjugated polymer for blue-light emitting devices [6] due to its high photoluminescence (PL) quantum yield; this is caused, in part, by the intrachain order in the film induced by the planarization of neighboring phenyl rings [7]. mLPPP was chosen as a model polymer because of its reduced inhomogeneity and small defect density [8].For the excitation beam in the PMAS measurements we used either an Ar 1 laser at several discrete E, or a monochromatized xenon lamp beam to continuously vary E between 2 and 4.5 eV. The excitation beam was modulated with a chopper at a frequency, f, between 10 to 4 kHz. A combination of various incandescent lamps, diffraction gratings, optical filters, and solid state detectors was used to span the probe energy (hv) between 0.1 and 3 eV. The PM spectrum as a function ofhv was obtained by dividing the pump beam induced changes in transmission, DT ͑v͒, by the probe transmission T ͑v͒, where Da 2d 21 DT ͞T and d is the film thickness; DT was measu...

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Section: Introductionmentioning

confidence: 99%

“…Kajzar et al [1] studied the dispersion of χ (3) in polyacetylene using the third order harmonic generation. They reported for the range of 1.17-1.5 eV a non resonant χ (3) value of ∼ 10 −10 esu. Sinclair et al [2] have performed a THG study of trans polyacetylene, and they reported a value of χ (3) = 4 × 10 −10 esu.…”

Section: Introductionmentioning

confidence: 99%

“…Sinclair et al [2] have performed a THG study of trans polyacetylene, and they reported a value of χ (3) = 4 × 10 −10 esu. A free electron laser was used by Fann et al [3] to measure the full spectrum of (761) the third order susceptibility. They found two peaks at 0.6 eV and 0.9 eV in the spectrum that are assigned to three-and two-photon resonance, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Third Harmonic Generation Susceptibility of Polyacetylene in Terms of the Chain Temperature

Sabra

2006

Acta Phys. Pol. A

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The tight binding Hamiltonian of Su, Schrieffer, and Heeger has been used to describe the physical properties of the polyacetylene chain. The chain temperature is calculated from the potential energy which is directly related to the CH group displacement. Two different forms of the displacements have been considered: random and Gaussian. The third harmonic generation susceptibility spectra have been plotted in terms of the temperature using the four-wave mixing formula. The results show that a second peak at the mid gap energy has occurred for room temperature which is in good agreement with the experimental data.

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Spectrum ofχ(3)(-3ω;ω,ω,ω) in polyacetylene: An application of free-electron laser in nonlinear optical spectroscopy

Cited by 236 publications

References 14 publications

Photogeneration and recombination processes of neutral and charged excitations in films of a ladder-type poly(para-phenylene)

Photogeneration and recombination processes of neutral and charged excitations in films of a ladder-type poly(para-phenylene)

Photogeneration Action Spectroscopy of Neutral and Charged Excitations in Films of a Ladder-Type Poly(Para-Phenylene)

Third Harmonic Generation Susceptibility of Polyacetylene in Terms of the Chain Temperature

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