1996 Fiscal Year Final Research Report Summary
Analysis of the Intermolecular Dynamics of Open-shell Radical Complexes
| Project/Area Number |
07454148
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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 |
ENDO Yasuki The University of Tokyo, Graduate School of Arts and Sciences, Associate Professor, 大学院・総合文化研究科, 助教授 (41016159)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Open-shell molecule / Molecular complex / Fourier-transform microwave spectroscopy / Double resonance spectroscopy / Molecular ion complex / Intermolecular interaction / Molecular orbital method |
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| Research Abstract |
Compared to the closed shell molecular complexes, molecular complexes containing open shell species species or ionic have little been studied by high-resolution spectroscopic methods. The present project intended to investigate these species by using Fourier-transform microwave spectroscopy or mm-wave/cm-wave double resonance spectroscopy in order to elucidate intermolecular interactions. Specific interest lies in the roles of the unpaired electron in the open shell species and the charge in the ionic species how they contribute to the intermolecular dynamics.
During the period of present research project, we observed rotational spectra of Ne-OH,Kr-OH,Ar-SH,H_2O-OH,H_2O-SH,Ar-HCO^+, and Kr-HCO^+ for the first time. Results of Ne-OH and Kr-OH and Kr-OH were analyzed by a method previously applied to the Ar-OH system, considering large amplitude motion of the OH moiety and the couplings of the spin and orbital angular momenta of the unpaired electron. The intermolecular interaction potent
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ials were compared with that of Ar-OH,and their differences were explained by considering the polarizabilities of the rage-gas atoms. Similar analysis has been applied to the analysis of Ar-SH.The resulting intermolecular potential for Ar-SH i quite different from those of Rg-OH systems : anisotropy around OH is much smaller than those of Rg-OH,undergoing large amplitude motion with larger amplitude.
Spectroscopic detections of H_2O-OH and H_2S-SH are important as these complexes are closely related to the understanding of the hydrogen exchange reactions. The observed spectrum of H_2O-OH was analyzed as the system is a doublet asymmetric rotor with the orbital angular momentum in OH completely quenched. The two hydrogen atoms in H_2O showed appreciable magnetic hyperfine splittings suggesting some delocalization of the unpaired electron on the OH radical. Theintermolecular distance was explained as the two constituents were bonded by the hydrogen bonding with OH proton to be proton donor. The spectrum of H_2S-SH showed many anomaly and detailed analysis is still under way.
The ionic complexes Ar-HCO^+ and Kr-HCO^+ were studied in detail including their various isotopomers, yielding precise determination of their molecular structure. The Rg-H distances thus obtained were much smaller than those of neutral complexes. They were well explained by considering a rather simple electrostatic model. The present results also agrees with large scale ab initio calculations including their intermolecular potentials indirectly estimated from the present experimental data.
In order to understand intermolecular, we performed ad initio molecular orbital calculations for these systems. We obtained fair agreements for H_2O-OH and ion complexes. We expect that molecular orbital calculations will help further understanding of the intermolecular intermolecular for such systems. Less
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