FIRST OBSERVATION OF DYNAMIC INTENSITY BORROWING INDUCED BY COHERENT MOLECULAR VIBRATIONS IN <font>J</font>-AGGREGATES REVEALED BY SUB-5-FS SPECTROSCOPY

Kano, Hiromi; Saitō, Takashi; Ueki, Akikatsu; KOBAYASHI, TAKAYOSHI

doi:10.1142/9789812811387_0058

Cited by 2 publications

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“…It leads to the conclusion that energy conservation is not satisfied within the single mode but energy flow takes place between the 1633 cm –1 mode and the 824 cm –1 mode through the low frequency 50 cm –1 mode. Such a dynamical modulation of coherent intramolecular vibration in J-aggregates was not previously observed for J-aggregates of pseudoisocyanine (PIC) and tetraphenylporphine tetrasulfonic acid (TPPS). − The low-frequency mode is presumably assigned to an intermolecular vibrational mode (lattice phonon mode of J-aggregates), which might be coupled to the electronic excitation of delocalized excitons.…”

Section: Discussionmentioning

confidence: 80%

“…However, it has yet to be determined how the structures of J-aggregates are correlated to their electronically excited states because of very weak exciton–phonon (intramolecular vibration) coupling in the Frenkel excitons of the J-aggregates. In fact, coherent molecular vibrations induced by electronic (excitonic) excitation have been observed only for aggregates of pseudoisocyanine (PIC) and tetraphenylporphine tetrasulfonic acid (TPPS). − …”

Section: Introductionmentioning

confidence: 99%

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Vibrational Energy Flow between Modes by Dynamic Mode Coupling in THIATS J-Aggregates

et al. 2013

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We performed ultrafast pump-probe spectroscopy of J-aggregates of 3,3'-disulfopropyl-5,5'-dichloro-9-ethyl thiacarbocyanine triethylammonium (THIATS), one of the most typical cyanine dyes, and detected excited molecular vibrations, using a sub-10 fs pulse laser. The time-resolved two-dimensional difference absorption (ΔA) spectra are observed between -314 and 1267 fs. By performing the Fourier transform and spectrogram analysis, vibrational modes in THIATS are observed at 285, 485, 555, 824, and 1633 cm(-1) and there was a modulation of the vibrational frequencies around 1633 cm(-1) which depend on the delay time, respectively. By the analysis of the modulation, energy flow is found to take place from other modes to the 1633 cm(-1) mode through the low frequency mode with ∼50 cm(-1). Also, by fitting the real-time traces of ΔA with the sum of two exponential functions and a constant term, the average lifetimes of three electronically excited states were found to be τ1 = 52 ± 5 fs and τ2 = 540 ± 78 fs. By performing single-exponential fitting around the stationary absorption peak at 1.990 eV, in the negative time range, the electronic dephasing time, T2(ele), is determined to be 18.30 fs.

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Section: Discussionmentioning

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Vibrational Energy Flow between Modes by Dynamic Mode Coupling in THIATS J-Aggregates

et al. 2013

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“…[44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63] The molecular motion induced by an intense, ultrashort light pulse gives rise to a quantum beat that is represented by the probe delay time (t)-dependent absorbance change δ A(t) in addition to the slow transient electronic absorbance change A(t) caused by the electronic processes of induced absorption, stimulated emission, and/or bleaching. [44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63] The molecular motion induced by an intense, ultrashort light pulse gives rise to a quantum beat that is represented by the probe delay time (t)-dependent absorbance change δ A(t) in addition to the slow transient electronic absorbance change A(t) caused by the electronic processes of induced absorption, stimulated emission, and/or bleaching.…”

Section: Vibrational Quantum Beat Spectroscopymentioning

confidence: 99%

“…These processes may include cascading four-wave mixing and the self-action induced by modulation of the refractive index by molecular vibration through vibronic coupling, which is not included in the coupled equations (52)- (56). These processes may include cascading four-wave mixing and the self-action induced by modulation of the refractive index by molecular vibration through vibronic coupling, which is not included in the coupled equations (52)- (56).…”

Section: Probing Processmentioning

confidence: 99%

Development of Ultrashort Pulse Lasers and Their Applications to Ultrafast Spectroscopy in the Visible and Nir Ranges

Kobayashi¹

2016

Advances in Multi-Photon Processes and Spectroscopy

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Both intensity-dependent nonlinear processes and field-only dependent processes are involved in the process of our discussion of ultrashort pulses Advances in Multi-Photon Processes and Spectroscopy Downloaded from www.worldscientific.com by UNIVERSITY OF OTTAWA on 09/11/16. For personal use only. Development of Ultrashort Pulse Lasers and their Applications 159in the visible range in this subsection. The former group includes SHG and OPA, and the latter includes SPM. For ultrashort pulse generation in the visible spectral range, including a part of the near infrared (NIR) range, the second-order nonlinear polarization effect has been used in a second-order nonlinear crystal without an inversion symmetry. Even though OPF can be used in principle to generate a pulse with a spectrum sufficiently broad to be an ultrashort pulse, it is too weak to have utility for some experimental purposes because it originates from vacuum noise; therefore, OPA is used instead of OPF to obtain a pulse of sufficient intensity. As mentioned previously, an intense pump light (ω p ) amplifies a weak signal (ω s ) without real population inversion in OPA process. In this case, the energy conversion is satisfied among the intense pump light, the weak signal of frequency ω s , and an idler of frequency ω I = ω p − ω s , which is generated simultaneously by means of second-order nonlinear polarization. An idler pulse is generated from a vacuum, which is coupled with the pump and associatively amplifies the signal at a frequency of ω s = ω p − ω i . The spatial and temporal overlaps of the three are needed to be maintained for efficient conversion. In the beginning, the intensity of the pump is much higher than that of signal, signal amplification continues along with pump propagation through the nonlinear crystal, and the energy of the pump photon is consequently divided into the signal photon and the idler photon. This process can be considered to be a parametric down-conversion (PDC) process from the high-frequency pump photon to the low-frequency signal and idler photons by means of an increase in the photon numbers of the signal and idler at the expense of the pump.As mentioned above, in the case of OPA, pump pulse, signal pulse, and idler pulse must meet the following angular frequency dependence:Here, ω j are the angular frequencies with the suffixes p, s, and i corresponding to the pump, signal, and idler, respectively. Since this is the relation among pulses the angular frequencies has some width corresponding to the inverse of the temporal shapes of the pulses. Here the angular frequencies are set to be the center frequencies. Because of the finite widths of the pulses, the relation of (5) has some ambiguity. The relation can be rephrased in the photon view. The corresponding to the three components in the OPA process Advances in Multi-Photon Processes and Spectroscopy Downloaded from www.worldscientific.com by UNIVERSITY OF OTTAWA on 09/11/16. For personal use only. Advances in Multi-Photon Processes and Spectroscopy Downloaded fr...

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FIRST OBSERVATION OF DYNAMIC INTENSITY BORROWING INDUCED BY COHERENT MOLECULAR VIBRATIONS IN J-AGGREGATES REVEALED BY SUB-5-FS SPECTROSCOPY

Cited by 2 publications

References 0 publications

Vibrational Energy Flow between Modes by Dynamic Mode Coupling in THIATS J-Aggregates

Vibrational Energy Flow between Modes by Dynamic Mode Coupling in THIATS J-Aggregates

Development of Ultrashort Pulse Lasers and Their Applications to Ultrafast Spectroscopy in the Visible and Nir Ranges

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