1997 Fiscal Year Final Research Report Summary
Real-time probing of Energy Dissipation Processes in Solvated Clusters
| Project/Area Number |
08454177
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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 | Kyoto University |
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Principal Investigator |
OHSHIMA Yasuhiro Kyoto Univ., Graduate School of Science, Associate Professor, 大学院・理科研究科, 助教授 (60213708)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Clusters / ps Time-Resolved Spectroscopy / Solvation / Energy Dissipation / Laser-Induced Fluorescence / Charge-Transfer / Inter-System Crossing |
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| Research Abstract |
The present research project aims to microscopic understanding on the energy dissipation processes in solvated clusters through ultrafast time-resolved measurements. Owing to the improvement in the experimental setup, such as the vacuum chambers and laser systems, the following results have been achieved.
1. The 1 : 1 cluster of 9,9'-bianthryl (BA) with water has been studied for detailed characterization of the twisted intramolecular charge transfer (TICT) reaction in BA.The torsional potential of BA in the cluster has been determined form the laser-induced-fluorescence observation of the torsional progressions. The potential in the cluster is much different from that in the monomer, indicating considerable modification in the electronic character of BA by complexation, as well as steric repulsion between BA and water. The ps time-resolved fluorescence measurements have shown that the TICT rate has no appreciable dependence on excitation energy or solvent isotopic substitution. This ob
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servation confirms that the TICT reaction proceeds via "sequential" mechanism ; the initially prepared level is predominately coupled to intermediate levels with high vibrational excitation of torsional motion, which further relax to the final levels in the charge-separated state. This result demonstrates the importance of the torsional motion in the dynamics of TICT reactions.
2. The water-solvated clusters of 9-acridone (AD) have been studied to explore the microscopic solvation effect on inter-system crossing (ISC) in AD.The fluorescence quantum yield is greatly enhanced with increasing order of solvation. Especially, drastic change with>200-fold increase caused by addition of only one water to the monomer indicates the crossover of the reaction mechanism form the direct ISC to the second-order ISC.Structural characterization by JR-UV double resonance spectroscopy combined with ab initio MO calculation has shown that water is hydrogen-bonded to C=O of AD in the 1 : 1 cluster. These results validates the site-selective microsolvation effect on ISC. Less
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