研究者詳細 - 中嶋　敦

論文 - 中嶋　敦

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Formation and structures of transition metal-C₆₀ clusters

S. Nagao, T. Kurikawa, K. Miyajima, A. Nakajima, K. Kaya

Journal of Physical Chemistry A （American Chemical Society） 102 （ 24 ） 4495 - 4500 1998年05月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 10895639

Transition metal (Sc, Ti, V, and Cr)-C60 binary clusters were produced in the gas phase by a two-laser vaporization method. In the mass spectra of cationic Mn(C60)m+, for M = Sc, Ti, and V, clusters having the composition of (n, m) = (1, 1)+, (1, 2)+, (2, 3)+, (3, 4)+, (4, 4)+, and (5, 5)+ were predominantly produced. The peaks having (n, n + 1)+ compositions are explicable in terms of multiple dumbbell structures, in which metal atoms and C60 are alternately stacked. Clusters with composition (4, 4)+ and (5, 5)+ are presumed to be ring structures. For Crn(C60)m+, however, a Cr atom is surrounded by three C60, forming a tricapped structure, and the structure acts as a unit for larger stable clusters of (2, 4)+, (3, 4)+, and (4, 4)+. Ionization energy measurements for neutral Mn(C60)m and a chemical probe method using CO, O2, and C2H4 as reactants gave information concerning the geometrical and electronic structures.

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Geometric and electronic structures of fluorine bound silicon clusters

R. Kishi, Y. Negishi, H. Kawamata, S. Iwata, A. Nakajima, K. Kaya

Journal of Chemical Physics （American Institute of Physics） 108 （ 19 ） 8039 - 8058 1998年05月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 0021-9606

Geometries and energies of SinF- and SinF (n=1-7) were investigated with ab initio MO calculations; the Møller-Plesset perturbation and coupled cluster methods were used to take into account the electron correlation. The F atom is bound to the apex atom in the Sin frame, and the electronic structures of the Sin part in SinF- and SinF are similar to those of the corresponding Sin and Si+n, respectively. The calculated electron affinities (EAs) of SinF are in agreement with the experimental values. The size dependence of EAs of SinF is similar to that of the ionization energies of Sin at n≥5, whereas it is different at n≤4. In the HOMO of SinF (n≤4), the weak antibonding nature between F and Si greatly makes the SinF- anions unstable, resulting in small EA. The vibrationally resolved photoelectron spectra (PES) of SinF- (n=1-3) were measured, and were completely reproduced theoretically. © 1998 American Institute of Physics.

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Formation of cobalt-C₆₀ clusters: Tricapped Co(C₆₀)₃ unit

T. Kurikawa, S. Nagao, K. Miyajima, A. Nakajima, K. Kaya

Journal of Physical Chemistry A （American Chemical Society） 102 （ 10 ） 1743 - 1747 1998年02月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 10895639

Cobalt (Co)-C60 mixed clusters were produced by the combination of laser vaporization and molecular beam methods. Cationic Con(C60)m+ clusters were produced predominantly with the compositions (n, m) = (0-1, 1), (1, 2), (1, 3), (2-4, 4), and (5, 5). Both mass spectrometry and a chemical probe method have revealed that compositions of (1, 3) and (4, 4) correspond to a tricapped planar structure and a tricapped trigonal pyramid structure, respectively, in which each Co atom is surrounded by three C60.

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Geometric and electronic structures of silicon-sodium binary clusters. II. Photoelectron spectroscopy of Si_nNa_m^- cluster anions

R. Kishi, H. Kawamata, Y. Negishi, S. Iwata, A. Nakajima, K. Kaya

Journal of Chemical Physics （American Institute of Physics） 107 （ 23 ） 10029 - 10043 1997年12月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 00219606

Electronic properties of silicon-sodium cluster anions (SinNam-,; 4≤n≤11, 1≤m≤3) were investigated by photoelectron spectroscopy using a magnetic-bottle type electron spectrometer. The electron affinities (EAs) of SinNam were determined from the threshold energies in the photoelectron spectra of SinNam-. Besides, the geometries and energies of SinNa- (n=1-7) were investigated with ab initio MO (molecular orbital) calculations; Møller-Plesset perturbation and coupled cluster methods were used to take into account the electron correlation. By an Na adsorption on Sin, the EA decreases for n=4-6, but increases for n≥7. The calculations for SinNa- show that the Sin framework for n=4-6 accepts at least two excess electrons. For Si7Na-, however, the charge transfer from the Na atom scarcely occurs to avoid distorting the close-packed Si7 framework. Moreover, the ionization energy (Ei) and EA of SinNam, show several patterns with the number of the Na atoms, which reflect the charge transfer mechanism in the cluster reflecting the nature of the electron-accepting orbitals of the corresponding Sin and the adsorption types of the Na atoms. © 1997 American Institute of Physics.

Ab initio MO studies of neutral and anionic SiC_n clusters (n = 2-5)

M. Gomei, R. Kishi, A. Nakajima, S. Iwata, K. Kaya

Journal of Chemical Physics （American Institute of Physics） 107 （ 23 ） 10051 - 10061 1997年12月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 00219606

The geometries and energies of SiCn and SiCn (n=2-5) were investigated with ab initia calculations including electron correlation effects with the MP2/6-31G* method, followed by MP4 and CCSD(T) single-point calculations to determine the most stable isomers. The adiabatic electron affinities (AEA) were evaluated with the ΔMP4 method. Because of the complexity of the electronic structure of SiC2, its AEA was calculated at the CCSD(T)/aug cc-pVTZ//CCSD(T)/aug cc-pVDZ level of approximation. For the neutral SiCn clusters, the isomer having a triplet ground state has large EA, whereas the isomer having a singlet ground state has small EA. This is attributed to the bonding character between Si and C atoms in the orbital occupied by the extra electron. The calculated EA was used to assign the photoelectron spectra of SiCn- reported previously. Furthermore, the effects of Renner-Teller splitting for the linear isomers of anions are discussed. © 1997 American Institute of Physics.

Study on iron-sulfur cluster in gas phase: Electronic structure and reactivity

A. Nakajima, T. Hayase, F. Hayakawa, K. Kaya

Chemical Physics Letters （Elsevier Science BV） 280 （ 3-4 ） 381 - 389 1997年12月

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

In gas phase, electronic and geometric properties of iron-sulfur cluster (FenSm, n=1-8, m=2-6) have been investigated using photoelectron spectroscopy (PES) of their anions and a chemical probe method for their cations. The electron affinities of FenSm greatly change at the composition of n=m, and the reactivity of FenSm+ toward NH3 and C2H2 is enhanced around equally mixed compositions. These results show that the FenSm clusters produced in gas phase seemingly take the structure having alternate bonds between Fe and S atoms, likewise that of an active site of iron-sulfur proteins.

Multiple dumbbell structures of vanadium-C₆₀ clusters

A. Nakajima, S. Nagao, H. Takeda, T. Kurikawa, K. Kaya

Journal of Chemical Physics （American Institute of Physics） 107 （ 16 ） 6491 - 6494 1997年10月

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

Vanadium (V)-C60 mixed clusters were produced by two laser vaporization methods. In the mass spectra of cationic Vn(C60)m+, the abundant clusters were produced at the composition of (n,m) = (1,1), (1,2) (2,3), (3-4,4), and (5,5). This pattern is explicable in terms of a multiple dumbbell structure V atom and C60 are alternatively piled up. The ionization energy and the reactivity of the dumbbell clusters toward O2 and CO show V1(C60)2 takes a structure of V1(η6 -C60)2. © 1997 American Institute of Physics.

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Geometric and electronic structures of silicon-sodium binary clusters. I. Ionization energy of Si_nNa_m

R. Kishi, S. Iwata, A. Nakajima, K. Kaya

Journal of Chemical Physics （American Institute of Physics） 107 （ 8 ） 3056 - 3070 1997年08月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 00219606

Sodium doped silicon clusters (SinNam; 1≤n≤14, 1≤m≤5) produced by two types of laser vaporization were studied. The adsorption of Na atoms on the Sin clusters leads the substantial lowering of the ionization energy, Ei, of SinNam clusters. Their reactivity toward NO molecules was measured with a fast flow reactor, and the anticorrelation between the Eis and the reactivity was clearly observed; species having low Ei exhibit high reactivity and vice versa. Moreover, the clear parallelism between the Eis of SinNa and the EAs of Sin is found. This is consistent with the fact that the structure of SinNa clusters keeps the frame of the corresponding Sin cluster unchanged and that the electronic structure of SinNa is similar to that of the corresponding negative ion Sin-. In addition to the experimental studies, the geometries, adsorption energies, and vertical ionization energies of SinNa (n = 1-7) were investigated with ab initio MO calculations including electron correlation; The Møller-Plesset perturbation theory was used and the configuration interaction (CI) calculation was carried out, particularly for a diatomic molecule, SiNa. © 1997 American Institute of Physics.

Why do vanadium atoms form multiple-decker sandwich clusters with benzene molecules efficiently?

T. Yasuike, A. Nakajima, S. Yabushita, K. Kaya

Journal of Physical Chemistry A （American Chemical Society） 101 （ 29 ） 5360 - 5367 1997年07月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 1089-5639

Transition-metal benzene clusters, Mn(benzene)m (M = Ti, V, and Cr), were synthesized by the reaction of laser-vaporized metal atoms with benzene vapor. All the clusters exhibit magic number behavior at m = n + 1, which is rationalized by the structure of a multiple-decker sandwich, but V atoms can efficiently take the sandwich structure (up to n = 5) in particular. This metal specificity of the V atoms and their growth mechanism were examined by quantum chemical calculations, the full valence configurational interaction (FVCI) method with configuration-averaged SCF Orbitals. The calculation results imply that (1) total spin conservation in growth process plays an important role and (2) the production in the sandwich clusters particularly favors a process through lower spin states. The combination between experimental and theoretical investigations leads us to a better comprehension of both the bonding scheme in the sandwich clusters and the growth mechanism, and accordingly, a more efficient production method is proposed generally for the transition-metal sandwich complexes.

Effect of ring substituents on formation rates for vanadium-arene clusters

M. Hirano, K. Judai, A. Nakajima, K. Kaya

Journal of Physical Chemistry A （American Chemical Society） 101 （ 27 ） 4893 - 4899 1997年07月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 1089-5639

Vanadium-arene complexes, Vn(arene)m (arene = benzene (C6H6), toluene (C6H5CH3), and fluorobenzene (C6H5F)), were synthesized by the reaction of laser-vaporized vanadium atoms with arene vapor. Both the analysis of the mass spectra and the measurements of their ionization energies indicate that both Vn(C6H5-CH3)m and Vn(C6H5F)m, clusters take a multiple-decker sandwich structure similar to the structure of Vn-(C6H6)m clusters. The relative reactivity between benzene and toluene toward vanadium was also determined; toluene is 4 times as reactive as benzene for V1(C6H5CH3)1/V 1(C6H6)1 production and 2 times for V1(C6H5-CH3)2/V 1(C6H6)2 production because of reactivity enhancement of the electron-donating ring substituent. In the case of the Vn(C6H5F)m cluster, it is found that the electron-withdrawing ring substituent of fluorobenzene results in much less reactivity than is observed for benzene and toluene.

Formation of vanadium-arene complex anions and their photoelectron spectroscopy

K. Judai, M. Hirano, H. Kawamata, S. Yabushita, A. Nakajima, K. Kaya

Chemical Physics Letters （Elsevier Science BV） 270 （ 1-2 ） 23 - 30 1997年05月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 0009-2614

Vanadium-arene complex anions, V1(arene)-m (m =1,2; arene = benzene, fluorobenzene, and toluene) were synthesized by the gas phase reaction of laser vaporized metal atoms with aromatic compound vapors. According to the 18-electron rule, it was anticipated that bis(benzene)vanadium should be stabilized by an electron attachment. However, it was experimentally concluded that bis(benzene)vanadium has negative electron affinity. The photoelectron spectra for the observed complex anions were measured, and the electronic configurations of metal-arene complexes and their structures are discussed.

Photoelectron spectroscopy of germanium-fluorine binary cluster anions: The HOMO-LUMO gap estimation of Ge_n clusters

Y. Negishi, H. Kawamata, T. Hayase, M. Gomei, R. Kishi, F. Hayakawa, A. Nakajima, K. Kaya

Chemical Physics Letters （Elsevier Science BV） 269 （ 3-4 ） 199 - 207 1997年05月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 00092614

Electronic properties of germanium-fluorine cluster anions (GenF-m; n = 1-11, m = 1-3) were studied using photoelectron spectroscopy (PES) with a magnetic-bottle type electron spectrometer. Compared between the PES of GenF- and those of the Ge-n, it was found that the doped F atom in GenF- deprives each Ge-n cluster of the excess electron without any serious rearrangement of the Gen framework. The F doping method enables us to estimate the HOMO-LUMO gap of the corresponding neutral Gen clusters (n = 4-11). For a diatomic GeF- cluster, furthermore, the vibrational structures could be resolved to determine its vibrational frequency.

Structures and stabilities of 3d-transition metal-benzene organometallic clusters

T. Kurikawa, H. Takeda, A. Nakajima, K. Kaya

Zeitschrift fur Physik D-Atoms Molecules and Clusters （Springer） 40 （ 1-4 ） 65 - 69 1997年03月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 0178-7683

In the gas phase, we have successfully synthesized organometallic clusters, Mn(benzene)m (M = 3d transition metal atoms), by using a laser vaporization method. The measurements of mass spectra and ionization energies (Ei) have revealed that the organometallic clusters can take two types of structures; layered sandwich structures (m = n + 1) and metal clusters saturatedly covered with benzenes. For early transition metals of Sc, Ti, and V, only the multiple decker sandwich structure clusters were preferentially produced, in which benzene and metal atoms are alternately piled up. For late transition metals of Co and Ni, the metal clusters saturatedly surrounded by benzenes were also produced as well as the sandwich clusters. Furthermore, the Eis of M1(benzene)2 (M = Sc-Ni) were systematically measured and their electronic properties will be discussed. © Springer-Verlag 1997.

Photoelectron spectroscopy of transition metal-sulfur cluster anions

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

Zeitschrift fur Physik D-Atoms Molecules and Clusters （Springer） 40 （ 1-4 ） 17 - 21 1997年03月

研究論文（学術雑誌）, 共著, 筆頭著者, 査読有り, ISSN 0178-7683

Metal (M)-sulfur cluster anions (M = Ag, Fe and Mn) have been studied using photoelectron spectroscopy (PES) with a magnetic-bottle type time-of-flight electron spectrometer. The MnS-m cluster anions were formed in a laser vaporization cluster source. For Ag-S, the largest coordination number of Ag atoms (nmax) is generally expressed as nmax=2m-1 in each series of the number of S atoms (m). For Fe-S and Mn-S, it was found that the stable cluster ions are the ones with compositions of n = m and n = m±1. Their electron affinities were measured from the onset of the PES spectrum. For Ag-S, the EAs of Ag1Sm are small and around 1 eV, whereas those of AgnSm (n ≥ 2) become large above 2 eV. The features in the mass distribution and PES suggest that Ag2S unit is preferentially formed with increasing the number of Ag atoms. For Fe-S and Mn-S, the PES spectra of FenS-m/MnnS-m show a unique similarity at n ≥ m, indicating that the Fe/Mn atom addition to FenS-n/MnnS-n has little effect on the electronic property of FenSn/MnnSn. The PES spectra imply that the FenSn cluster is the structural framework of these clusters, as similarly as the determined structure of the FenSn cluster in nitrogenase enzyme. © Springer-Verlag 1997.

Photoelectron spectroscopy of silicon- and germanium-fluorine binary cluster anions (Si_nF_m^-,Ge_nF_m^-)

K. Kaya, H. Kawamata, Y. Negishi, T. Hayase, R. Kishi, A. Nakajima

Zeitschrift fur Physik D-Atoms Molecules and Clusters （Springer） 40 （ 1 ） 5 - 9 1997年03月

研究論文（学術雑誌）, 共著, 最終著者, 査読有り, ISSN 01787683

Electronic properties of silicon-fluorine and germanium-fluorine cluster anions (SinF-m; n = 1-9, m = 1-3, GenF-m; n=1-9, m=1-3) were investigated by photoelectron spectroscopy using a magnetic-bottle type electron spectrometer. The binary cluster anions were generated by a laser vaporization of a silicon/germanium rod in an He carrier gas mixed with a small amount of SiF4 or F2 gas. Comparison between photoelectron spectra of SinF-/GenF- and Si-n/Ge-n (n=4-9) gives the insight that the doped F atom can remove one electron from the corresponding Si-n/Ge-n cluster without any serious rearrangement of Sin/Gen framework, because only the first peak of Si-n/Ge-n, corresponding singly occupied molecular orbital (SOMO), disappears and other successive spectral features are unchanged with the F atom doping © Springer-Verlag 1997.

High-resolution laser-induced fluorescence spectra of 7-azaindole-water complexes and 7-azaindole dimer

A. Nakajima, M. Hirano, R. Hasumi, K. Kaya, H. Watanabe, C. C. Carter, J. M. Williamson, T. A. Miller

Journal of Physical Chemistry A （American Chemical Society） 101 （ 4 ） 392 - 398 1997年01月

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

The geometric structures of 7-azaindole-water complexes, (7-AzI)-(H2O)n (n = 1-3), and 7-AzI dimer were investigated by laser-induced fluorescence (LIF) spectroscopy with high resolution (∼0.01 cm-1). For the 7-AzI-(H2O)n complexes (n = 1-3), the LIF spectra show partially resolved rotational structure, which has been analyzed in combination with theoretical calculations. This analysis yields the rotational constants and characterizes the structures. In 7-AzI-(H2O)1, the H2O molecule is located in the molecular plane, forming a six-membered ring with two hydrogen bonds. Analyses for 7-AzI-(H2O)2 and -(H2O)3 show, furthermore, that both the second and the third H2O are located in the molecular plane of 7-AzI, forming a network ring of hydrogen bonds. For the 7-AzI dimer, the LIF spectrum shows an unresolved rotational envelope. The rotational contour has been analyzed, and we discuss the dimer's likely structure.

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Geometric and electronic structure of binary clusters containing silicon atoms

K. Kaya, A. Nakajima

Materials Science and Engineering: A （Elsevier Science BV） 217/218 7 - 11 1996年10月

研究論文（学術雑誌）, 共著, 最終著者, 査読有り, ISSN 09215093

Photoelectron spectroscopy of silicon-fluorine binary cluster anions (Si_nF_m^-)

H. Kawamata, Y. Negishi, R. Kishi, S. Iwata, A. Nakajima, K. Kaya

Journal of Chemical Physics （American Institute of Physics） 105 （ 13 ） 5369 - 5376 1996年10月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 0021-9606

<p>Electronic properties of silicon-fluorine cluster anions (Si_nF_m^-; n=1-11, HZ = 1-3) were investigated by photoelectron spectroscopy using a magnetic-bottle type electron spectrometer. The binary cluster anions were generated by a laser vaporization of a silicon rod in an He carrier gas mixed with a small amount of SiF₄ or F₂ gas. The highly abundant clusters are SiF_m^- (m=3 and 5) and Si_nF^- (n=6, 7, and 10) in their mass spectra. In the photoelectron spectra of SiF_m^- (m = 1-5), the clusters having odd m have higher electron affinity (EA) than those having even in, indicating that the even/odd alternation in EA is attributed to their electronic structures of a closed/open valence shell. Comparison between photoelectron spectra of Si_nF^- and Si_n^- (n=4-11) gives the insight that the doped F atom can remove one electron from the corresponding Si_n^- cluster without any serious rearrangement of Si_n^- framework, because only the first peak of Si_n^-, corresponding singly occupied molecular orbital (SOMO), disappears and other successive spectral features are unchanged with the F atom doping. In some clusters, furthermore, the vibrational structures could be resolved to determine a vibrational frequency and to presume the geometry with ab initio molecular orbital calculations.</p>

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Theoretical study of carbon doped small silicon clusters: Electron affinities of Si_nC (n = 2-5)

R. Kishi, M. Gomei, A. Nakajima, S. Iwata, K. Kaya

Journal of Chemical Physics （American Institute of Physics） 104 （ 21 ） 8593 - 8604 1996年06月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 00219606

The geometries and energies of SinC and SinC- (n=2-5) were investigated with ab initio MO calculations including electron correlation. The Møller-Plesset perturbation theory was used for n=3-5. The configuration interaction (CI) calculations were carried out for n=2 and 3. The most stable isomers of the neutral SinC clusters have the structure in which an Si atom having the largest sp hybridization in the corresponding Sin+1 cluster is replaced by a C atom. For their anions, the structures in which an excess electron is distributed avoiding a C atom become stable. Moreover, the adiabatic electron affinities of SinC and vertical detachment energies of anionic SinC- were computed. They reproduced the trends of photoelectron spectra of SinC- reported previously. © 1996 American Institute of Physics.

Theoretical Study of Silicon-M Binary Clusters（M=C and Na）

R. Kishi, A. Nakajima, S. Iwata, K. Kaya

T. Kondow et al.（eds.）”Structures and Dynamics of Clusters” frontiers science series （Universal Academy Press）（ 16 ） 607 - 612 1996年05月

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