2006 Fiscal Year Final Research Report Summary
Laser spectroscopic study on model negative ion systems of biological electron-transfer reaction intermediates
| Project/Area Number |
17550006
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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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 | Tohoku University |
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Principal Investigator |
MAEYAMA Toshihiko Tohoku University, Graduate School of Science, Research associate, 大学院理学研究科, 助手 (20250673)
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| Project Period (FY) |
2005 – 2006
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| Keywords | NEGATIVE ION / INFRARED SPECTROSCOPY / PHOTOELECTRON SPECTROSCOPY / ELECTRON DETACHMENT / ELECTRON TRANSFER / HYDROGEN BOND / SOLVATION |
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| Research Abstract |
Size-dependent features of the electron localization in negatively charged formamide clusters (FA_n^-, n=5-21) have been studied by photodetachment spectroscopy. In the photoelectron spectra for all the sizes studied, two types of bands due to different isomers of anions were found. The low binding energy band peaking around 1 eV is assigned to the solvated electron state by relative photodetachment cross-section measurements in the near-infrared region. It is suggested that nascent electron trapping is dominated by formation of the solvated electron. The higher energy band originates from the covalent anion state generated after a significant relaxation process, which exhibits a rapid increase of electron binding energy as a function of the cluster size. A unique behavior showing a remarkable band intensity of the higher energy band was found only for n=9. In addition, vibrational spectra of microsolvated benzonitrile radical anions (C_6H_5CN-S; S=H_2O and CH_3OH) were measured by probing the electron detachment efficiency in the 3μm region, representing resonance bands of autodetachment via OH stretching vibrations of the solvent molecules. The hydrogen-bonded OH band for both the cluster anions exhibited a large shift to the lower energy side with approximately 300 cm^<-1> comparing to those for the corresponding neutral clusters. The solvent molecules are bound collinearly to the edge of the CN group of the benzonitrile anion in the cluster structures optimized with the density functional theory, in which the simulated vibrational energies are in good agreement with the observed band positions. Natural population analyses were performed for a qualitative implication in changes of solvent orientation upon electron attachment.
Asymmetric band shapes depending on the vibrational modes are discussed with respect to dynamics of the autodetachment process from a theoretical aspect incorporated with density functional calculations.
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Research Products
(4 results)
