S. Kinoshita

LOW FREQUENCY MODES PROBED BY TIME-DOMAIN OPTICAL KERR EFFECT SPECTROSCOPY

The principle and application of ultrafast optical Kerr effect (OKE) spectroscopy have been reviewed. This spectroscopy is shown to be very useful to investigate low frequency modes in disordered materials and the obtained data are directly comparable with frequency-domain light scattering spectroscopy. Experimental study to show the consistency between the time- and frequency-domain spectroscopy has been performed for liquid nitrobenzene and the excellent agreement is attained over three orders of magnitude in frequency range. It is also shown that the result obtained by the OKE measurement is consistent with that obtained by four wave mixing spectroscopy. Combination of these spectroscopic techniques is particularly suited for the investigation of low frequency modes because a wide frequency range is covered with great accuracy. Several remarks concerning the OKE spectroscopy are presented such as the breakdown of Debye relaxation model and various interference effects which may distort the time-domain ...

Efficient optical Kerr shutter for femtosecond time-resolved luminescence spectroscopy

We have measured optical Kerr effect responses, transmission spectra, and emission properties due to two photon absorption for 17 kinds of optical glass materials and have evaluated their capabilities as an optical Kerr shutter (OKS) for time-resolved luminescence spectroscopy. There is a tendency that the larger the refractive index and dispersion are, the higher the electronic response of optical Kerr effect becomes. Transmission efficiency as high as several percents with the time resolution of 350 fs is obtained using a highly Bi2O3-doped glass plate under 200 kHz repetitive pulse excitation. The time-resolved luminescence spectrum of Zn-tetraphenylporphyrin dye solution is demonstrated using the combination of the OKS and a monochromator equipped with a charge coupled device detector.

Direct comparison of femtosecond Fourier-transform Raman spectrum with spontaneous light scattering spectrum

Abstract We have performed high-resolution light scattering and ultrafast optical Kerr effect experiments on liquid samples and have compared both data by using the time-domain Fourier-transform. Complete agreement has been obtained in the frequency range from 3 GHz to 6 THz. This is the first report in which these time- and frequency-domain data are directly compared.

Transient hole‐burning and time‐resolved fluorescence spectra of dye molecules in solution: Evidence for ground‐state relaxation and hole‐filling effect

A picosecond transient hole‐burning (THB) spectroscopy has been performed for organic dyes in solution. The THB spectra of rhodamine 640 have been found to show a time‐dependent spectral change. This phenomenon corresponds to the solvent relaxation effect observed in the time‐resolved fluorescence (TRF) spectrum. Although TRF spectrum is related only to the excited‐state relaxation, THB spectrum is affected by both ground‐ and excited‐state relaxations. Comparing with the TRF spectrum measured under the same exciting energy, we have clarified the presence of the ground‐state relaxation. Further, the THB spectrum of styryl‐8 gives an antihole between well‐separated two holes corresponding to ground‐ and excited‐state contributions. This may originate from the hole‐filling effect due to the nonadiabatic relaxation from the nonequilibrium excited state to the ground state. The analysis based on a configuration coordinate model gives an overall understanding for these phenomena.

Solvent relaxation effect on transient hole-burning spectra of organic dyes

Abstract Picosecond transient absorption spectra of organic dyes in solution are measured at room temperature. When a dye molecule is dissolved in viscous solvents, a transient spectrum initially shows a slightly sharp hole around the exciting energy, accompanied by the time-dependent broadening of its shape. This phenomenon corresponds to the solvent relaxation effect reported frequently in time-resolved fluorescence spectroscopy.

Light scattering study of liquid and plastic phases of succinonitrile from 0.003 to 3000 cm−1

Abstract Light scattering spectra of liquid and plastic phases of succinonitrile have been measured around the phase transition temperature for a wide frequency range using a Sandercock-type tandem Fabry–Perot interferometer and a double monochromator. Although the molecular structures in these two phases have been found similar, the spectral difference becomes prominent with decreasing frequency. Particularly, the onset of the difference lies in the so-called low-frequency modes ( −1 ), implying that the cooperativity among various modes is essential for the manifestation of macroscopic nature.

New high-resolution phonon spectroscopy using impulsive stimulated Brillouin scattering

Impulsive stimulated Brillouin scattering is applied to a new high‐resolution phonon spectroscopy, where phonons created by two crossing pump pulses are observed using diffraction of a cw probe light in both time and frequency domains. In time domain, real‐time behavior can be detected sensitively using a digital oscilloscope, while in frequency domain, measurements with high resolution are attainable by means of a spherical Fabry–Perot interferometer. Several examples of the measurements on liquid samples are demonstrated for clarifying various aspects of the phonon generation by the present method: the mechanism of the generation under pulsed light irradiation, the propagation of the generated phonon, the resonance excitation, and the interference with the other nonlinear optical processes. The relation with the ordinary light scattering is also discussed.

Ultrafast fluorescence spectroscopy of photoactive yellow protein

Using the optical Kerr shutter method, room temperature time-resolved fluorescence spectroscopy of photoactive yellow protein (PYP) has been performed. Spectral profiles of the time dependent fluorescence have been measured as snapshots with high time resolution of about 300 fs. For the first time, spectral narrowing in the ps-time region was directly observed, which is consistent with the previously reported results of the faster decay on both sides of the fluorescence peak.

Direct comparison between femtosecond optical Kerr effect and high-resolution light scattering measurements

Abstract We have performed optically heterodyne-detected optical Kerr effect measurement for transparent liquids with ultrashort light pulses. In addition, the depolarized low-frequency light scattering measurement has been performed by means of a double monochromator and a high-resolution Sandercock-type tandem Fabry-Perot interferometer. The frequency response functions obtained from the both data have been directly compared. They agree perfectly for a wide frequency range. This results is the first experimentaa evidence for the equivalence between the time- and frequency-domain measurements.

Relation between Stokes and anti-Stokes low-frequency light scattering in liquid carbon disulfide

Abstract The intensity ratio of Stokes to anti-Stokes light scattering in the low-frequency region ( −1 ) has been investigated within an accuracy of ∼0.01 for liquid carbon disulfide at 292 K. The spectrum shows a symmetric lineshape about the excitation frequency in the region less than several wavenumber, indicating that the commonly used relation between these scattering intensities based on canonical distribution breaks down in this frequency region. The symmetric lineshape of the spectrum may arise from its dissipative character.