Relaxation dynamics of photoexcitations in polydiacetylenes and polythiophene

Kobayashi, Takayoshi; Yoshizawa, M.; Stamm, Uwe; Taiji, Makoto; Hasegawa, Masamitsu

doi:10.1364/josab.7.001558

Cited by 230 publications

(117 citation statements)

References 75 publications

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“…This is attributed to rapid cooling of the initially excited population in the first excited state (polaron band) as in PD-PANI. The profile of the intermediate state absorption, ε 3 , shown in Figure 12C, is red-shifted compared with that of PD-PANI and looks very similar to the profile of ε 10 . This suggests that transient absorption from the intermediate, similar to PA2 absorption of PD-PANI, can be hidden under the more prominent red-shifted bleaching/stimulated emission.…”

Section: Kinetic Modeling Of Relaxationmentioning

confidence: 63%

Ultrafast Dynamics of Polarons in Conductive Polyaniline: Comparison of Primary and Secondary Doped Forms

2008

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Time-and wavelength-resolved pump-probe measurements are performed on the conductive, primary and secondary doped, forms of polyaniline in solution to investigate the relaxation dynamics of photoexcited polarons. Contrasting dynamics observed in the two forms allow investigation of electronic (and structural) relaxation of this material. Pump pulse at 800 nm photoexcites an electron from the valence to polaron band, and subsequent relaxation dynamics are probed by a white light continuum pulse. Three distinct features are observed in the primary doped sample: (1) absorption near time zero in the 900-1025 nm probe wavelength region; (2) delayed absorption from 850 to 1025 nm; (3) pronounced oscillations with frequencies of 165 and 210 cm -1 . The first two features are associated with intraband absorptions to higher-lying states in the polaron band from the initial excited and conformationally changed intermediate states. The oscillations reflect torsional motions associated with photoexcitation and relaxation. In the secondary doped material, only bleaching and stimulated emission are observed throughout the whole spectral region; neither transient absorption signals nor oscillatory dynamics are observed. Kinetic modeling is performed to establish the mechanism of relaxation. We propose that the excited polaron relaxes nonradiatively to the ground state through an intermediate state(s) with a twisted geometry. Our measurements and analysis allow us to describe the structure of the polaron bands for primary and secondary doped polyaniline; they are in the small and large polaron limits, respectively, and are consistent with a bandgap for the primary doped form and without a bandgap (i.e., metallic) for the secondary doped material.

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Section: Kinetic Modeling Of Relaxationmentioning

confidence: 63%

Ultrafast Dynamics of Polarons in Conductive Polyaniline: Comparison of Primary and Secondary Doped Forms

2008

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“…Details are described in the previous section and in [59][60][61][62]. photo-excitation, where a conversion from one state to the other is occurring.…”

Section: Methodsmentioning

confidence: 99%

Ultrafast spectroscopy of coherent phonon in carbon nanotubes using sub-5-fs visible pulses

Kobayashi¹

2016

AIP Conference Proceedings

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“…Additionally, owing to the pulse length of approximately 80 fs, the time resolution is at the limit for this experiment as the dynamics of the electronic excited PES are very fast. 31,128,129 In order to separate the chirp effect in this experiment, non-resonant femtosecond time-resolved CARS measurements are in preparation.…”

Section: Spectroscopy In the Time Domainmentioning

confidence: 99%

A review on linear and non‐linear resonance Raman spectroscopy of the conjugated system polydiacetylene

Materny

Chen

Vierheilig

et al. 2001

J Raman Spectroscopy

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We review resonance Raman investigations of the linear conjugated p-electron system of polydiacetylenes embedded in single-crystalline monomer matrices. Absorption, luminescence, resonance Raman and resonance CARS spectroscopy were used to investigate vibronic properties of the polymers. As an example, we discuss the theoretical model applied for the simulation of the resonance Raman line and excitation profiles obtained from the polymer chains in FBS, TS/FBS and TS6 diacetylene single crystals. The theory is based on a Franck-Condon model, which considers a chain length dependence. The electronic transition energies and matrix elements were calculated by means of an LCAO MO (linear combination of atomic orbitals molecular orbital) calculation in the Hückel approach. An interaction between ensemble and intramolecular properties due to defects can be shown. Besides the well known polymer absorption, the partially polymerized single crystals of the diacetylenes under investigation show blue-shifted absorption bands in sharply separated crystal areas. The spectroscopic investigations of this chromism revealed that most probably growth defects in f111g crystal growth sectors influence the side-group geometry of the polymer chains. Using femtosecond time-resolved CARS spectroscopy, the dynamics of the vibrational excitation in the electronic ground and excited states can be investigated. Here, we report the controlled selective excitation of the polymers. We used a CARS scheme where the difference of pump and Stokes laser wavelengths is chosen to achieve resonance with several chain modes of the polydiacetylenes. By varying the timing and the phases of the femtosecond laser pulses, the timing and the intensity of these modes can be strongly influenced.

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Relaxation dynamics of photoexcitations in polydiacetylenes and polythiophene

Cited by 230 publications

References 75 publications

Ultrafast Dynamics of Polarons in Conductive Polyaniline: Comparison of Primary and Secondary Doped Forms

Ultrafast Dynamics of Polarons in Conductive Polyaniline: Comparison of Primary and Secondary Doped Forms

Ultrafast spectroscopy of coherent phonon in carbon nanotubes using sub-5-fs visible pulses

A review on linear and non‐linear resonance Raman spectroscopy of the conjugated system polydiacetylene

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