2004 Fiscal Year Final Research Report Summary
Experimental exploration of structural transformation of isolated small many-body systems
| Project/Area Number |
14340180
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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 | Institute for Molecular Science (2004)
Kyoto University (2002-2003) |
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Principal Investigator |
OHSHIMA Yasuhiro Institute for Molecular Science Dept. of Electronic Structure, Professor, 電子構造研究系, 教授 (60213708)
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| Project Period (FY) |
2002 – 2004
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| Keywords | gas-phase cluster / structural transformation / intermolecular vibration / structural isomer / femto-second time-resolved spectroscopy / laser multiple resonance / intermolecular potential |
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| Research Abstract |
This research project aims at deeper understanding on structural phase transformation, such as melting, via experimental exploration on isolated gas-phase clusters, which are typical systems with limited number of degrees of freedom. We have planned to characterize their energy-level structure of vibrations pertinent to structural transformation by utilizing laser spectroscopy, and to probe in real time the motion of molecules along with the structural transformation by femto-second time-resolved spectroscopy. We have achieved experimental data on some important systems and developed a new experimental method, as follows.
1) Electronic spectra of benzene clusters have been reexamined by using mass-selective resonance-enhanced ionization. In contrast that hexamer and the smaller clusters exhibit sharp vibronic bands, the larger clusters show broad absorption. This observation implies the coexistence of many structural isomers and/or large structural fluctuation for the larger clusters. Sudden change in the morphology of potential energy surfaces pertinent to structural transformation may occur at this cluster size.
2) Clusters containing aromatic molecules with protic solvents, i.e., anthracene-ammonia and benzene-water, have been studied. Weak vibronic bands pertinent to intermolecular modes have been observed with good S/N by utilizing laser double resonance. The present data will be essential to construct the intermolecular potential with high accuracy.
3) A time-resolved spectroscopic method in femto-second regime has been developed for real-time probing of structural transformation motions. The versatility of the method have been demonstrated by the successful observation of vibrational and rotational wavepackets of various molecules. In particular, wavepacket of the internal-rotation of a methyl group has been observed for the first time.
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