| Budget Amount *help |
¥55,900,000 (Direct Cost: ¥55,900,000)
Fiscal Year 2000: ¥4,300,000 (Direct Cost: ¥4,300,000)
Fiscal Year 1999: ¥4,600,000 (Direct Cost: ¥4,600,000)
Fiscal Year 1998: ¥47,000,000 (Direct Cost: ¥47,000,000)
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| Research Abstract |
We have developed two new light sources and spectroscopic techniques in the infrared region to investigate the chemical reactions and relaxation phenomena in condensed phases under this project. One is the third order optical nonlinear spectroscopy in the infrared region using intense femtosecond infrared pulses. The infrared pulses are generated by some optical nonlinear processes such as difference frequency mixing and optical parametric generation/amplification. Group velocity dispersion in the pulse is compensated by inserting a silicon plate in the optical path. The pulse width is measured to be 55 fs with an energy of more than microJ/pulse by an autocorrelation method, which is the shortest pulse of the infrared pulse with such a high energy to our knowledge. Using this pulse we have constructed optical systems of nonlinear spectroscopy such as transient grating, 2- and 3-pulse photon echo including frequency-resolved version. The frequency-resolved 3-pulse photon echo is one of
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the two-dimensional vibrational spectroscopies. We have applied these techniques to several vibrational modes such as three-atom ions (OCN^- and SCN^-) in polar solvents, the -N=C=N- antistretching modes of large organic molecules, the C=O stretching modes of metal porphyrines, and the CN stretching modes of cyano-iron complexes. We discuss vibrational dynamics of these modes including vibrational population relaxation, pure vibrational dephasing, dynamical fluctuation and spectral diffusion, inhomogeneity of the transition frequency, and so on. The other technique we have developed is a spectroscopic method using terahertz (THz) radiation. The THz radiation is generated by focusing a femtosecond pulse to a semiconductor wafer and amplified by applying a magnetic field to the wafer. The THz radiation is detected by an electro-optic sampling method. By using spectrometer in the far-infrared region with the THz radiation as a light source, we have measured far-infrared absorption spectra of various kinds of condensed phase systems such as bulk liquids, solutions of charge-transfer complexes, biopolymers, and so on. Especially, far infrared spectra of polypeptides and proteins (cytochrom c) were studied in detail, and we discuss relation between structures of the biopolymers and spectra in the low-frequency region. Less
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