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Studies on microscopic solvation process of alkali-metal atoms and NH4 radical in clusters
https://ir.soken.ac.jp/records/288
https://ir.soken.ac.jp/records/288f83f03cf-7f4c-4a3f-8c66-0eb2051a5f6a
| 名前 / ファイル | ライセンス | アクション |
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要旨・審査要旨 / Abstract, Screening Result (320.8 kB)
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本文 / Thesis (15.6 MB)
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| Item type | 学位論文 / Thesis or Dissertation(1) | |||||
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| 公開日 | 2010-02-22 | |||||
| タイトル | ||||||
| タイトル | Studies on microscopic solvation process of alkali-metal atoms and NH4 radical in clusters | |||||
| タイトル | ||||||
| タイトル | Studies on microscopic solvation process of alkali-metal atoms and NH4 radical in clusters | |||||
| 言語 | en | |||||
| 言語 | ||||||
| 言語 | eng | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_46ec | |||||
| 資源タイプ | thesis | |||||
| 著者名 |
高須, 良三
× 高須, 良三 |
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| フリガナ |
タカス, リョウゾウ
× タカス, リョウゾウ |
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| 著者 |
TAKASU, Ryozo
× TAKASU, Ryozo |
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| 学位授与機関 | ||||||
| 学位授与機関名 | 総合研究大学院大学 | |||||
| 学位名 | ||||||
| 学位名 | 博士（理学） | |||||
| 学位記番号 | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | 総研大甲第258号 | |||||
| 研究科 | ||||||
| 値 | 数物科学研究科 | |||||
| 専攻 | ||||||
| 値 | 08 機能分子科学専攻 | |||||
| 学位授与年月日 | ||||||
| 学位授与年月日 | 1997-03-24 | |||||
| 学位授与年度 | ||||||
| 値 | 1996 | |||||
| 要旨 | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | 1. Introduction Electrons and metal ions in fluids play important roles in many aspects of chemical phenomena and have been the subject of numerous investigations for many years. Although experimental and theoretical studies have attempted to understand the nature and the dynamics of solvation for these species, its microscopic aspect has not yet been fully understood. Recently, advances in molecular beam technique open new approaches to a microscopic investigation of the excess electrons and metal ions in fluids. The clusters containing neutral metal atoms and/or its ions have found to be easily produced in a beam. The study of successively large clusters is analogous to modeling the process of solvation and provides them information on microscopic solvation. The purpose of this study is to get insights into the electron delocalizaion, the formation of solvation shell, and the fundamental interactions among ions, solvent molecules, and electrons via the observation of the physical and chemical properties of the gas-phase clusters containing metal atoms and its tons as a function of number of solvent molecules. He also examined the solvated NH4 radicals which are isoelectronic with alkali-metals. 2. Microscopic solvation process of alkali-atom in clusters; photoelectron and photoionization studies of M(NH3)n and M(H20)n(M=Li, Li-, Na-) Photoelectron spectra(PESs) of Li-(NH3)n(n〓16), Na- (NH3)n(n〓12) and Na- (H2O)n(n〓7), as well as the ionization potentials (IPs) of Li(NH3)n(n〓28) and Li(H2O)n(n〓46), are examined. PESs of Li-(NH3)n(n〓14) exhibit three bands derived from the Li(3 2S)-Li-(1S), Li(2 2P)-Li-(1S), and Li(2 2S)-Li-(1S) transitions. The vertical detachment energies (VDEs) of the 3 2S and 2 2P-type states decrease dramatically with increasing n. In addition to these observations, he also finds the redshift of the neutral ground (2 2S) state with much slower rate. For n〓10, the transitions to the 2P-and 2S-type states are almost superimposed each other. The similar spectral trends are also observed for the Na(3 2P)-Na-(1S)and Na(3 2S)-Na-(1S) transitions of Na-(NH3)n. On the other hand, the transitions of Na-(H2O)n exhibit an opposite shifts with maintaining the 2P-2S energy separation. As for Li(H2O)n, he finds a monotonous decrease in IPs with n〓4 and a constant IP behavior for n〓5. The limiting value for n→∞(3.12 eV) coincides with the photoelectric threshold of ice as in the case of Cs(H2O)n and Na(H2O)n. Based on the results of ab initio calculations, he discusses these experimental findings in connection with the early stage of solvated-electron formation in finite clusters. 3. Microscopic solvation process of sodium dimer in ammonia clusters; photoelectron spectra of Na2(NH3)n- Photoelectron spectra of Na2(NH3)n(n=0-8) are investigated in relation to the microscopic solvation process of sodium dimer in small ammonia clusters. Na2(NH3) exhibits four bands at the vertical detachment energy (VDE) of 0.41, 1.36, 2.11 and 2.40 eV, corresponding to the transitions from the anion state to the neutral ground and excited states derived from the X1Σg+, a3Σu+, b3IIu, and A1Σu+ states of Na2, respectively. The VDEs of the neutral ground state for n〓8 are almost the same as that of Na2(1Σg+), while that of the first excited state derived from the Na2(3Σu+) increases gradually for n〓4. In addition, the 3IIu- and 1Σu+-type transitions are found to shift rapidly to lower VDE and degenerate into the 3Σu+-type transition. He discusses the solvation state of Na2 in (NH3)n with present results of experiments and theoretical calculations . 4. Formation and microscopic solvation process of NH4 radical NH4 is a typical hypervalent Rydberg radical and its spectroscopic properties have been extensively studied since the first spectroscopic characterization by Herzberg. Although NH4 was first well characterized with spectroscopy in the gas phase, the existence of mercury amalgam has long been anticipated. The possible existence of NH4 radical in the reaction of the solvated electron and in electrochemistry has also been speculated on for many years. If NH4 exists as solvated species in the condensed phase, an interesting question is raised how the Rydberg orbital is affected by the presence of large number of other molecules the radical is expected to have a diffuse electronic structure. Since NH4 is isoelectronic with alkali atoms, the ammoniated NH4 clusters may serve as a new testing material to get further insight into the electron localization modes in the gas-phase clusters. Moreover, the study on the stability of these clusters as a function of the number of solvent molecules may provide them some clues to reveal the aforementioned long standing problems in bulk solution.<br />Formation process of NH4 radical in ammonia clusters Photochemical reaction of ammonia clusters in the first excited state is studied by a femtosecond pump-probe technique and a time-of-flight mass spectroscopy. Small ammonia clusters containing NH4 radical are probed by resonance enhanced two-photon ionization method. NH4 radical is formed within 0.5 ps and decomposes with a lifetime of 13 ps. The ammonia dimer ion is found to be formed mainly through the one-photon ionization of a new photolysis product such as an excited-state NH4*-NH2. This intermediate may correspond to a cage product in the predissociation process of larger ammonia clusters and its formation and decay times are ca. 1 ps and < 1 ns, respectively. He also examined the lifetimes of NH4(NH3)n using the pump-probe technique with nanosecond lasers. The lifetime of NH4 is found to be elongated more than 10 6 times in ammonia clusters. The mechanism of the formation and decay processes for these species are discussed on the basis of the present results in conjunction with the theoretical results in literatures. Electronic structure and stability of NH1 (NH3)n Ammoniated NH4 radicals produced by an ArF excimer laser photolysis of ammonia clusters are studied by one-photon ionization and time-of-flight mass spectroscopy. The ionization potentials (IPs) of NH4(NH3)n(n=0-35) are determined by the photoionization threshold measurements. The binding energies of NH4(NH3)n-1 -NH3(n=1-6) are estimated from IPs. The results indicate that the bonding between NH4 and NH3 is semi-ionic. The IPs for larger clusters are found to decrease monotonically with increasing n to a limit of 1.33 eV, which coincides with the photoemission threshold of liquid NH3. This feature is similar to those found for alkali atoms-ammonia clusters. Electronic structure and stability of NH1(NH3)m(H2O)n The photoionization process of NH4(NH3)m(H2O)n radicals produced by an ArF excimer laser photolysis of ammonia-water mixed clusters are examined using a time-of-flight mass spectroscopy. The ionization potentials (IPs) of NH4(NH3)m(H2O)n(m=0-4, n=0-3) are determined by the photoionization threshold measurements. A clear trend is found for the IPS: the clusters containing more water molecules have higher IP. This trend is ascribed to the large binding energy of NH4+-NH3 comparing with that for NH4+-H2O. |
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| 所蔵 | ||||||
| 値 | 有 | |||||
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| 内容記述タイプ | Other | |||||
| 内容記述 | application/pdf | |||||
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| 出版タイプ | AM | |||||
| 出版タイプResource | http://purl.org/coar/version/c_ab4af688f83e57aa | |||||
