研究者詳細 - 中嶋　敦

論文 - 中嶋　敦

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Photoelectron spectroscopy of cobalt oxide cluster anions

A. Pramann, K. Koyasu, A. Nakajima, K. Kaya

Journal of Physical Chemistry A （American Chemical Society） 106 （ 19 ） 4891 - 4896 2002年04月

研究論文（学術雑誌）, 共著, 責任著者, 査読有り, ISSN 1089-5639

Photoelectron spectroscopy of size-selected ConOm- clusters (n = 4-20; m = 0-2) is performed in a pulsed molecular beam experimental at photon energies of 3.49 and 4.66 eV. Cobalt oxide cluster anions are generated in a laser vaporization source and the photoelectron spectra are measured with a magnetic bottle photoelectron spectrometer. The size-dependent evolution of the electronic structure of the oxide clusters is discussed in terms of cluster composition. Threshold binding energy features are mainly contributed from Co d-derived orbitals throughout the complete series, indicating that the incoming oxygen atoms cause a minor influence on the electronic structures. Although for n > 13 EAs and VDEs of Con and ConOm clusters overlap within the experimental resolution, at smaller cluster sizes, the values increase in the order of Con < ConO < ConO2. For Co4O3- and Co5O3-, the spectra indicate the presence of isomers with low EAs peroxo and ozonide isomers. To compare the different channels of oxygen chemisorption, relative dissociation energies are determined via thermochemical cycles.

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Anion photoelectron spectroscopy of V_nO_m^- (n = 4-15; m = 0-2)

A. Pramann, K. Koyasu, A. Nakajima, K. Kaya

Journal of Chemical Physics （American Institute of Physics） 116 （ 15 ） 6521 - 6528 2002年04月

研究論文（学術雑誌）, 共著, 責任著者, 査読有り, ISSN 00219606

Anion photoelectron spectroscopy was used to study small negatively charged vanadium oxide clusters at 4.66 eV photon energy. The electronic structure of the vanadium clusters was investigated as a function of size n and composition m. The changes of the electronic structure of the vanadium cluster cores after adding two oxygen atoms were examined. Thermomechanical cycles were used to determine relative dissociation energies for different oxygen-loss channels from the parent clusters. Electron affinities and vertical detachment energies were found to increase with increasing cluster size.

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Behavior of silicon and germanium clusters on a C₆₀ fullerene

M. Ohara, Y. Nakamura, Y. Negishi, K. Miyajima, A. Nakajima, K. Kaya

Journal of Physical Chemistry A （American Chemical Society） 106 （ 18 ） 4498 - 4501 2002年04月

研究論文（学術雑誌）, 共著, 責任著者, 査読有り, ISSN 10895639

Behavior of silicon (Si) and germanium (Ge) atoms (or clusters) on the surface of a C60 fullerene has been revealed by using time-of-flight mass spectroscopy and photoelectron spectroscopy. The mixed clusters of C60Sin and C60Gem were generated by two-lasers vaporization of a molded C60 rod and a Si (or a Ge) rod in He carrier gas. The size distributions of anionic and cationic C60Sin/C60Gem clusters monotonically decreased with the number of Si/Ge atoms, and were limited only up to n = 4 and m = 3. The photoelectron spectra of C60Sin- and C60Gem- are similar to that of pure C60- at m = 3, 4, whereas the spectra at n, m = 1, 2 are different from that of C60-. These results show that Si/Ge atoms assemble together into Si/Ge clusters on the C60 cage with an increase in the number of Si/Ge atoms.

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Anion photoelectron spectroscopy of vanadium-doped cobalt clusters

Pramann A., Koyasu K., Nakajima A., Kaya K.

Journal of Physical Chemistry A （AMER CHEMICAL SOC） 106 （ 11 ） 2483 - 2488 2002年03月

研究論文（学術雑誌）, 査読有り, ISSN 1089-5639

Bimetallic cobalt (Co)-vanadium (V) clusters, ConVm- (n = 4-14, m = 0-2), are investigated using anion photoelectron spectroscopy at 4.66 eV photon energy. Electron affinities (EA) and vertical detachment energies (VDE) are determined, and the electronic structures of V- and V2-doped Con clusters are compared to those of pure Con clusters. Bonding and hybridization effects can be explained using a charge-transfer model. A peak shape analysis confirms the high stability of the Co12V cluster with a most plausible icosahedral structure with the V atom in the cage center. Together with ionization potentials (IP), the electronic structures of the clusters are compared to H2 chemisorption rate coefficients reported previously. Thus, this study completes the investigation of electronic properties and reactivity of the bimetallic ConVm clusters as a function of charge, size, and distribution. Although the reactivity of ConVm reveals a better correlation toward the EA rather than toward IP, no improved correlation is found between promotion energies and reactivity. This result clearly shows that the chemisorption reactivity of the heterogeneous clusters is largely governed by geometric factors.

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Geometric and electronic structures of terbium-silicon mixed clusters (TbSi_n; 6 ≤ n ≤ 16)

M. Ohara, K. Miyajima, A. Pramann, A. Nakajima, K. Kaya

Journal of Physical Chemistry A （American Chemical Society） 106 （ 15 ） 3702 - 3705 2002年03月

研究論文（学術雑誌）, 共著, 責任著者, 査読有り, ISSN 10895639

The geometric and the electronic structures of terbium-silicon anions, TbSin- (6 ≤ n ≤ 16) were investigated by using photoelectron spectroscopy (PES) and a chemical-probe method. The clusters were produced by a double-rod laser vaporization technique. From trends observed in the electron affinities (EAs), the TbSin- clusters were categorized into three groups of (I) 6 ≤ n ≤ 9, (II) n = 10, 11, and (III) n ≥ 12. Together with adsorption reactivity toward H2O it is concluded that a Tb atom is encapsulated inside a Sin cage at n ≥ 10; Tb@Sin.

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A Novel Network Structure of Organometallic Clusters in Gas Phase

A. Nakajima, K. Kaya

E. Buzaneva and P. Scharff (eds.) “Frontiers of Multifunctional Nanosystems” (NATO Science Series, Series II. Vol. 57) Kluwer Academic Publishers （Springer Netherlands）（ 57 ） 173 - 190 2002年

研究論文（研究会，シンポジウム資料等）, 共著, 筆頭著者, 責任著者, 査読有り

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Comparison of hydrogen chemisorption rates and electronic structures of small Nb_nAl^- clusters: A photoelectron spectroscopic study

A. Pramann, A. Nakajima, K. Kaya

Chemical Physics Letters （Elsevier Science BV） 347 （ 4-6 ） 366 - 372 2001年10月

研究論文（学術雑誌）, 共著, 責任著者, 査読有り, ISSN 00092614

Photodetachment photoelectron spectroscopy experiments on NbnAl- clusters have been carried out in a size range n=4 to 12 at 3.49 eV photon energy. The evolution of the electronic structure is discussed as a function of cluster size and composition. Electron affinities (EA) and vertical detachment energies are determined. One central point of this study is the direct comparison of the electronic structure of pure and Al-doped Nbn- clusters in the threshold binding energy region with regard to hybridization effects. Direct correlation between electronic structure and H2 chemisorption rate constants reported by Nonose et al. [Chem. Phys. Lett. 164 (1989) 427], is found for n=5 to 8 and n>9. © 2001 Elsevier Science B.V.

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Photoelectron spectroscopy of V_x(coronene)_y and Ti_x(coronene)_y anions

M. A. Duncan, A. Knight, Y. Negishi, S. Nagao, K. Judai, A. Nakajima, K. Kaya

Journal of Physical Chemistry A （American Chemical Society） 105 （ 44 ） 10093 - 10097 2001年10月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 10895639

Gas-phase anion complexes are produced containing one or more vanadium or titanium atoms bound to one or more molecules of the polycyclic aromatic hydrocarbon (PAH) coronene (C24H12). These species are prepared with coincident laser vaporization of a metal rod and a pressed pellet of coronene in a pulsed-nozzle cluster source. The anion complexes produced are mass-selected with a time-of-flight spectrometer and photoexcited with various Nd:YAG laser harmonics. A magnetic bottle instrument is employed for time-of-flight photoelectron spectroscopy measurements on these complexes. Electron affinities (EA's) are observed to be greater for the organometallic complexes than they are for the isolated metal clusters or the isolated coronene molecule. EA's increase with the number of metal atoms in the complex. The spectra observed for V-coronene complexes are similar in appearance to those seen previously for V-benzene and V-C60, suggesting that the metal binds as a π complex in a symmetric ring site. V-(coronene)2 complexes exhibit different spectra under different conditions attributed to the formation of sandwich and external-metal isomers.

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Non-destructive selection of geometrical isomers of the Al(C₆H₆) cluster by a 2 m electrostatic hexapole field

K. Imura, T. Kawashima, H. Ohoyama, T. Kasai, A. Nakajima, K. Kaya

Physical Chemistry Chemical Physics （Royal Chemical Society） 3 （ 17 ） 3593 - 3597 2001年10月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 14639076

A supersonic cluster beam containing isomers of Al(C6H6) complexes was generated by laser evaporation, and non-destructively selected using a 2 m long electrostatic hexapole. The focusing curve shows clear evidence that there are two kinds of Al(C6H6) isomers which are slightly different from each other in geometry; one is an asymmetric 1,2-complex and the other nearly C6v symmetric 1,4-complex. The electric dipole moments of the two isomers are found to be 1.5 ± 0.1 and 1.4 ± 0.1 D, respectively. We carried out computation using density functional theory in order to estimate their structures. We found that the 1,2-complex is more stable than the 1,4-complex. The present work confirms that the electrostatic hexapole technique is useful for non-destructive selection of geometrical isomers in a beam.

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Mass spectra and photoelectron spectroscopy of negatively charged benzene clusters, (benzene)_n^- (n = 53-124)

M. Mitsui, A. Nakajima, K. Kaya, U. Even

Journal of Chemical Physics （American Institute of Physics） 115 （ 13 ） 5707 - 5710 2001年10月

研究論文（学術雑誌）, 共著, 責任著者, 査読有り, ISSN 00219606

The threshold size and photoelectron study of neat negatively charged benzene clusters was carried out using a high-temperature and high-pressure valve to generate cold, large, negatively charged benzene clusters. It was found that there is an abrupt onset of formation of the (benzene)n- clusters occurring at size n=53, and the cluster distribution extended to above n>160. Benzene clusters smaller than the threshold size were also observed. Photoelectron spectroscopy revealed that the VDES of (benzene)n- with n = 53-124 fell within 0.4-0.6 eV.

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Photoelectron spectroscopy of bimetallic aluminum cobalt cluster anions: Comparison of electronic structure and hydrogen chemisorption rates

A. Pramann, A. Nakajima, K. Kaya

Journal of Chemical Physics （American Institute of Physics） 115 （ 12 ） 5404 - 5410 2001年09月

研究論文（学術雑誌）, 共著, 責任著者, 査読有り, ISSN 00219606

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Photoelectron spectroscopy of gold-silver binary cluster anions (Au_nAg_m^-; 2 ≤ n + m ≤ 4)

Y. Negishi, Y. Nakamura, A. Nakajima, K. Kaya

Journal of Chemical Physics （American Institute of Physics） 115 （ 8 ） 3657 - 3663 2001年08月

研究論文（学術雑誌）, 共著, 責任著者, 査読有り, ISSN 00219606

The photoelectron spectra of the small Au-Ag mixed clusters produced by the laser vaporization of their alloy rod were observed. It was found that in their anions, the replacement of an Ag atom by an Au atom accompanies a preferable substitution to accept the excess charging electron. In triatomic Au-Ag clusters, Au atoms existed as a terminal atom. Evidence was obtained that in tetratomic Au-Ag clusters, isomers can coexist due to the contribution from an ionic bonding character.

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Photoelectron spectroscopy of yttrium oxide cluster anions: Effects of oxygen and metal atom addition

A. Pramann, Y. Nakamura, A. Nakajima, K. Kaya

Journal of Physical Chemistry A （American Chemical Society） 105 （ 32 ） 7534 - 7540 2001年07月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り, ISSN 10895639

The photoelectron spectra of small gas-phase YnOm- clusters (n = 2-10, m = 1-3) are measured at photon energies of 3.49 and 4.66 eV. Cluster generation is performed with the aid of laser vaporization, whereas the kinetic energy of electrons is measured using a magnetic bottle photoelectron spectrometer. The evolution of the electronic structure of neutral yttrium oxide clusters is discussed in terms of both sequential oxygen addition to the metal cluster core and sequential metal atom increase. Electron affinities and vertical detachment energies are measured and compared to ionization potentials of the monoxide cluster series [Knickelbein, M. J. Chem. Phys. 1995, 102, 1]. A general trend in the observed photoelectron spectra is a shifting of threshold energies to higher binding energies with increasing cluster size n. At low electron binding energies, main spectral features are contributed from metal d-band orbitals whereas the O 2p contribution becomes apparent with increasing oxygen content due to a higher degree of hybridization of yttrium s, d, and oxygen 2p orbitals. The differences of yttrium-oxygen dissociation energies are determined and compared.

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Electronic and geometric properties of exohedral sodium- and gold-fullerenes

B. Palpant, Y. Negishi, M. Sanekata, K. Miyajima, S. Nagao, K. Judai, D. M. Rayner, B. Simard, P. A. Hackett, A. Nakajima, K. Kaya

Journal of Chemical Physics （American Institute of Physics） 114 （ 19 ） 8459 - 8466 2001年05月

研究論文（学術雑誌）, 共著, 責任著者, 査読有り, ISSN 0021-9606

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Electronic properties of substituted aluminum clusters by boron and carbon atoms (Al_nB_m^-/Al_nC_m^-); New insights into s-p hybridization and perturbed shell structures

H. Kawamata, Y. Negishi, A. Nakajima, K. Kaya

Chemical Physics Letters （Elsevier Science BV） 337 （ 4-6 ） 255 - 262 2001年04月

研究論文（学術雑誌）, 共著, 最終著者, 査読有り, ISSN 00092614

Substituted Al clusters with B atom, which is trivalent but smaller than Al atom, or with covalent C atom were investigated using photoelectron spectroscopy (PES). In Aln-mBm- (n≥5 for m=1, n≥10 for m=2), three valence electrons of each B atom as well as Al atom contribute to electron shell structures, while the C atom strongly binds two free electrons from Aln- in AlnC- (n=5-30). The substitution with B atom allowed us to determine that s-p mixing starts at n=6 in pure Al clusters. Perturbed electron shells and the geometry of Al12B1-,Al11B2-, and Al12C- are discussed. © 2001 Elsevier Science B.V.

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Novel Electronic and Geometric Properties in Sub-nanometer Clusters

K. Kaya, M. Hashimoto, A. Kato, Y. Nakamura, K. Miyajima, Y. Negishi, S. Nagao, A. Nakajima

Proceeding of Nobel Symposium “The Physics and Chemistry of Clusters” （World Scientific） 278 - 290 2001年04月

研究論文（研究会，シンポジウム資料等）, 共著, 最終著者, 査読有り

In the gas phase, novel network structures were found in organometallic clusters between metal atoms and C-60. Lanthanide organometallic clusters, Ln(n)(C-60) consisting of lanthanide atoms (Ln; Ln = Eu and Ho) and C60 molecules were produced predominantly at compositions of (n, m)=(n, n+3) [n= 1 -4). The cluster having (1, 4) composition is proposed to form a tetrahedral structure, in which a Ln atom is surrounded by four C60 molecules. Together with the results of sequential chemisorption of Cl atoms on cluster cations, photoelectron spectroscopy of cluster anions leads us to conclude that Lnn(C-60)(m) clusters are charge transfer complexes expressed as Ln(n)(x+)(C-60)(m)(x-), and that Eu and Ho atoms exist as Eu2+ and Ho3+ ions. Furthermore, the electronic and geometric properties of gas-phase exohedral NanC60 and AunC60 cluster are investigated. For NanC60, the high stability of the n=3, 6, 9, and 12 anions was observed, which suggests a "wet" structure having these atoms packed into stable trimers on the surface. In contrast, the electron affinity of AunC60 clearly shows even-odd alternation with the number of Au atoms, which suggests a "dry" structure where An atoms are segregated from each other.

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A soft-landing experiment on organometallic cluster ions: Infrared spectroscopy of V(benzene)₂ in Ar matrix

K. Judai, K. Sera, S. Amatsutsumi, K. Yagi, T. Yasuike, S. Yabushita, A. Nakajima, K. Kaya

Chemical Physics Letters （Elsevier Science BV） 334 （ 4-6 ） 277 - 284 2001年02月

研究論文（学術雑誌）, 共著, 責任著者, 査読有り, ISSN 00092614

Vanadium (V)-benzene cluster ions, produced by laser ablation with reaction toward benzene vapor, were size-selected and deposited into a low-temperature Ar matrix. Infrared spectrum of V1(benzene)2 in the Ar matrix was measured after one-hour deposition with the deposition energy of 20 eV. The spectrum was in agreement with both the reported spectrum and our theoretical calculations, showing that (1) V1(benzene)2, prepared in the gas-phase reaction, takes a sandwich structure and that (2) the ions were soft-landed onto the Ar matrix and were neutralized by charge transfer from a metal substrate without fragmentation. © 2001 Elsevier Science B.V.

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Photoelectron spectroscopy of scandium-arene complex anions

K. Judai, Y. Nakamura, M. Tachibana, Y. Negishi, A. Nakajima, K. Kaya

Chemistry Letters （Chemical Society of Japan） 30 （ 2 ） 114 - 115 2001年02月

研究論文（学術雑誌）, 共著, 責任著者, 査読有り, ISSN 0366-7022

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Visible Photoluminescence from Deposited Germanium-Oxide Clusters

A. Nakajima, Y. Negishi, Y. Nakamura, K. Kaya

B. K. Rao, S. M. Bose, M. P. Das, and S. N. Sahu (eds.) “Science and Technology of Nanostructured Materials” （Nova Science Publishers, Inc.） 175 - 190 2001年

研究論文（研究会，シンポジウム資料等）, 共著, 筆頭著者, 責任著者, 査読有り

Optical properties of the deposited germanium-oxide (Ge-O) prepared from precursors of the Ge-O clusters were investigated. The strong visible photoluminescence peaked at 500 nm was observed under the excitation of 325 nm laser light, when the GenOn clusters were deposited onto a substrate as a precursor. The XPS spectrum of the deposited Ge-O on the substrate shows the contribution from the oxidation state of Ge2+, which shows that 1:1 composition of Ge2+-O2- is a key factor to exhibit the visible emission. Correspondingly, the electronic structures of the germanium-oxide cluster precursors produced by a laser vaporization were studied by using photoelectron spectroscopy (PES) for GenOm- and GenOmF- (n=2-6, m=1-5) in the gas phase. Our development of the halogen atom doping method enables us to determine the HOMO-LUMO gap of the corresponding neutral GenOn clusters experimentally, and it was found that the gap of the GenOn (n=2-5) clusters reasonably corresponds to the energy of the visible light. These results indicate that the GenOn clusters can be ascribed to the center of the visible photoluminescence.

Visible photoluminescence of the deposited germanium-oxide prepared from clusters in the gas phase

Y. Negishi, S. Nagao, Y. Nakamura, A. Nakajima, S. Kamei, K. Kaya

Journal of Applied Physics （American Institute of Physics） 88 （ 10 ） 6037 - 6043 2000年11月

研究論文（学術雑誌）, 共著, 責任著者, 査読有り, ISSN 0021-8979

Optical properties of the deposited germanium-oxide (Ge-O) prepared from the laser ablation of GeO2 were investigated. When the GenOm clusters, having the compositions mainly at n = m, were deposited onto a substrate as a precursor, strong visible photoluminescence peaked at 500 nm was observed under the excitation of 325 nm laser light. X-ray photoelectron spectroscopy for the deposited Ge-O on the substrate consistently shows the substantial component of the oxidation state of Ge2+, which shows the contributions from 1:1 composition of Ge2+-O2-. Correspondingly, the electronic structures of the germanium-oxide cluster were studied by using photoelectron spectroscopy in gas phase. Our developed method of the halogen atom doping enables us to determine the highest occupied molecular orbital-the lowest unoccupied molecular orbital gap of the corresponding neutral GenOn clusters experimentally, and it was found that the gap of the GenOn (n = 2-5) clusters reasonably corresponds to the energy of the visible light. These results imply that the GenOn clusters can be ascribed to the origin of the visible photoluminescence. © 2000 American Institute of Physics.

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中嶋 敦

論文 - 中嶋 敦

中嶋　敦

論文 - 中嶋　敦