2002 Fiscal Year Final Research Report Summary
Basic measurements of partial orders in solution
| Project/Area Number |
12440158
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical chemistry
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| Research Institution | The University of Tokyo |
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Principal Investigator |
IWATA Koichi The University of Tokyo, Graduate School of Science, Associate Professor, 大学院・理学系研究科, 助教授 (90232678)
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| Project Period (FY) |
2000 – 2002
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| Keywords | micelle / SDS / trans-stilbene / solution / carbon tetrachloride / diffusion-controlled reaction / femtosecond / time-resolved near-infrared spectroscopy |
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| Research Abstract |
Kinetics of bimolecular chemical reactions between trans-stilbene or biphenyl and carbon tetrachloride have been measured with femtosecond time-resolved spectroscopic methods. The observed kinetics are well explained by theories of diffusion-controlled reactions. This result suggests that the translational motion of molecules in solution is described well as diffusion motion after a few picosecond time interval.
Mechanism of a double proton transfer reaction induced by photoexcitation of the 2-aminopyridin / acetic acid complex has been examined. Experimental results from picosecond time-resolved spectroscopy show that this double proton transfer proceeds with a stepwise mechanism. It is crucial to keep the molecular complex between 2-aminopyridine and acetic acid for at least a few picoseconds for this reaction.
Temperature dependence of the trans-cis isomerization rate as well as the shape of the Raman bands of the first excited singlet (S_1) state of trans-stilbene have been measured in three different solvents, hexane, octane, and decane. The relation between the isomerization reaction rate and the solute-solvent interaction is discussed based on the experimental results. The dynamic polarization model, which postulates that the amplitude, duration, and frequency of the solute-solvent interaction determine both the reaction rate and the Raman band shape, explains the experimental results successfully.
Trans-stilbene solubilized in the hydrophobic core of the SDS micelle is ionized by photoexcitation. From the picosecond time-resolved CARS experiments, it has been suggested strongly that the generated cation radial reaches the outer hydrophilic interface between the micelle and the bulk water within 20 ps. It has been also suggested, however, that it takes 1 to 2 ps for the electron generated simultaneously with the cation radial to reach the bulk water.
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