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Your search keyword '"Kondow, T."' showing total 274 results
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274 results on '"Kondow, T."'

1. Spatial distribution of ions in a linear octopole radio-frequency ion trap in the space-charge limit

Author

Majima, T., Santambrogio, G., Bartels, C., Terasaki, A., Kondow, T., Meinen, J., and Leisner, T.

Subjects
Physics - Atomic and Molecular Clusters, Physics - Plasma Physics
Abstract

We have explored the spatial distribution of an ion cloud trapped in a linear octopole radio-frequency (rf) ion trap. The two-dimensional distribution of the column density of stored silver dimer cations was measured via photofragment-ion yields as a function of the position of the incident laser beam over the transverse cross section of the trap. The profile of the ion distribution was found to be dependent on the number of loaded ions. Under high ion-loading conditions with a significant space-charge effect, ions form a ring profile with a maximum at the outer region of the trap, whereas they are localized near the center axis region at low loading of the ions. These results are explained quantitatively by a model calculation based on equilibrium between the space-charge-induced potential and the effective potential of the multipole rf field. The maximum adiabaticity parameter \eta_max is estimated to be about 0.13 for the high ion-density condition in the present octopole ion trap, which is lower than typical values reported for low ion densities; this is probably due to additional instability caused by the space charge., Comment: 8 pages, 5 figures

Published
2012
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7. Collision-induced reactions of size-selected cluster ions of Ar

Author

Kondow, T., Nonose, S., Hirokawa, J., Ichihashi, M., Araki, H., editor, Brézin, E., editor, Ehlers, J., editor, Frisch, U., editor, Hepp, K., editor, Jaffe, R. L., editor, Kippenhahn, R., editor, Weidenmüller, H. A., editor, Wess, J., editor, Zittartz, J., editor, Beiglböck, W., editor, Schmidt, Rüdiger, editor, Lutz, Hans O., editor, and Dreizler, Reiner, editor

Published
1992
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31. Photodissociation dynamics of Ar+3.

Author

Ikegami, T., Kondow, T., and Iwata, S.

Subjects
*PHOTODISSOCIATION, *ARGON
Abstract

The nonadiabatic trajectory calculations were performed for the photodissociation process of Ar3+. Two methods—hemiquantal dynamics and Tully’s surface-hopping method—were applied and the results were compared. The calculated velocities of the photofragments had slow and fast bimodal distributions, as were experimentally observed. The ratio of the slow Ar+ fragment to the fast one decreased with the excitation wavelength, also in good agreement with the experimental results. It was shown that the slow component of Ar+ was produced only through the nonadiabatic transition during the photoissociation process, and that the nonadiabatic transition was dependent on the excitation energy. In addition, the vibrational motion, especially the bending motion, was shown to play an important role in the nonadiabatic process. [ABSTRACT FROM AUTHOR]

Published
1993
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32. Studies on dynamics of Mu reaction with NO2 by muon spin resonance and relaxation techniques.

Author

Sugai, T., Sakamoto, M., Matsushita, A., Nishiyama, K., Nagamine, K., and Kondow, T.

Subjects
MUON spin rotation, ISOTOPES, MAGNETIC fields
Abstract

The reaction of Mu with NO2 in a Kr atmosphere was studied by muon spin resonance and relaxation measurements at 300 K. It was found that the reaction proceeds via the following two steps: Mu+NO2→MuO+NO and MuO+NO2→MuNO3. In particular, the final product MuNO3 and the intermediate species MuO were successfully detected for the first time by the techniques of the muon spin resonance and the longitudinal relaxation under a high magnetic field of ∼2800 G. The rate constants of the Mu+NO2 and the MuO+NO2 reactions were determined to be (2.9±0.5)×1011 l mol-1 s-1 and (4.5±0.1)×109 l mol-1s-1 at 300 K. The isotope effect in the rate constant of the Mu+NO2 reaction in comparison with the H+NO2 reaction suggests that there are reaction paths with a slight energy barrier which is high enough to retard the H reaction, but not the Mu reaction. On the other hand, the rate constant of the MuO+NO2 reaction is smaller than 50% of those of the OH+NO2 and the OD+NO2 reactions. This isotope effect seems to originate from faster rotational motion of MuO and/or lower vibrational density of states at the transition state. [ABSTRACT FROM AUTHOR]

Published
1994
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35. Electronic States of Cobalt Cluster Cations : Absorption Spectrum of d Electrons and Spin-polarized DV-Xα Calculation

Author

Minemoto, S., Terasaki, A., and Kondow, T.

Subjects
Cobalt cluster ion, magnetism, Physics::Atomic and Molecular Clusters, optical absorption spectrum, Condensed Matter::Strongly Correlated Electrons, photodissociation, spin-polarized DV-Xα method
Abstract

Photodissociation spectra of cobalt cluster ion-argon atom complexes, Co^+_nAr (n=3-5), were measured by detecting the product ions Co^+_n and Co^+_, with a tunable laser pulse from an optical parametric oscillator in the photon-energy range from 0.7 to 2.8 eV. The photodissociation spectra thus obtained are equivalent to the optical absorption spectra of the underlying cobalt cluster ions, Co^+_n, because the argon atom is weakly bound to Co^+_n. The spectrum was analyzed by means of a spin-polarized DV-Xα calculation, and the electronic and the geometric structures of Co^+_3 and Co^+_4 were determined. The analysis shows that all the transitions in the entire energy range studied occur between occupied and unoccupied energy levels associated with 3d atomic orbitals (AOs) having the minority spin. The spin difference (difference in population per Co atom between the majority and the minority spins) was evaluated from the electronic structures thus obtained. The spin differences of 2.00 for Co^+_3 and 1.75 for Co^+_4 indicate ferromagnetic spin coupling in these cobalt cluster ions.

Published
1996

36. Electronic Structure of Vanadium Cluster Anions : Measurement and DV-Xα Calculation of Photoelectron Spectra

Author

Iseda, M., Nishio, T., Yoshida, H., Terasaki, A., and Kondow, T.

Subjects
vanadium cluster anions, photoelectron spectrum, electronic structure, DV-Xα method
Abstract

Photoelectron spectra of vanadium cluster anions, V^-_n(3≤n≤100), were measured at the photon energy of 3.49 eV by using a magnetic-bottle-type photoelectron spectrometer. A spin-polarized DV-Xα method was adopted to calculate electronic structures of V^-_4 with several possible geometric structures. These calculated spectra were compared with that obtained by the experiment to examine a geometric structure and magnetic properties of V^-_4. It is revealed that V^-_4 is spin-polarized and has ferromagnetic spin coupling. Size-dependent change in electronic affinities of V^-_4 is explained in terms of a spherical conducting droplet model.

Published
1996

39. Production of Heterogeneous Cluster, Ar_m(CO_2), by the Molecular Exchange Reaction of Ar_n with CO_2

Author

Ozaki, Y., Fukuyama, T., Ichihashi, M., and Kondow, T.

Subjects
molecular exchange reaction, binary cluster, Ar_mCO_2, trajectory calculation
Abstract

Molecular exchange reaction of an argon cluster Ar_n (n=6, 8, 11 and 14), in collision with a CO_2 molecule was investigated by computer simulation. Binary clusters, Ar_mCO_2, were found to be produced in the molecular exchange reaction, where m≤n. The cross sections for the reaction were calculated to be 21-29, 19-38, 37-46 and 71-107Å^2 for Ar_n (n=6, 8, 11 and 14), respectively, where the temperature of Ar_n was 20-40 K. The average numbers of released Ar atoms in the reaction, n-m, were also calculated. The cross sections and the numbers of released Ar atoms were almost consistent with those measured by the mass spectrometry of the products of Ar_n+CO_2 reaction using a cluster-beam gas-cell method.

Published
1996

41. Gas phase ion formation from a liquid beam of arginine in aqueous solution by IR multiphoton excitation

Author

Kohno, J., Toyama, N., Buntine, Mark, Mafuné, F., Kondow, T., Kohno, J., Toyama, N., Buntine, Mark, Mafuné, F., and Kondow, T.

Abstract

A liquid beam of aqueous solutions of arginine (AH), its hydrochloric acid salt (AH2Cl) and its sodium salt (ANa) was irradiated with a pulsed IR laser at 3509 cm−1 (2.85 μm). Positive and negative ions ejected to the gas phase were mass analyzed. From the AH2Cl and the ANa aqueous solutions, the pre-existing ions in the solution were ejected directly to the gas phase. From the AH solution, on the other hand, both a protonated arginine ion, AH2+ and an argininate ion, A− were observed in the gas phase. Production of these ions is accounted for the four-photon excitation of water molecules in the solution.

Published
2006

45. Size-specific reactions of transition metal clusters in collision with simple molecules.

Author

Ichihashi, M., Hanmura, T., Yadav, R. T., and Kondow, T.

Subjects
COMPLEX ions, METAL clusters, NICKEL, COLLISIONS (Physics)
Abstract

Reactions of nickel cluster ions, Ni[sub n][sup +] (n=3-11), with methanol molecules, CH[sub 3]OH, were studied at collision energies less than 1.0 eV by use of a tandem-type mass spectrometer. It was found that size-dependent chemisorption, demethanation and carbide formation of CH[sub 3]OH proceed on Ni[sub n][sup +]; the demethanation proceeds on Ni[sub 4][sup +], while the carbide formation on Ni[sub 7][sup +] and Ni[sub 8][sup +]. The initial steps of the reactions are physisorption and chemisorption of methanol on Ni[sub n][sup +]. The size dependence was explained in terms of kinematics on a reaction potential and the geometrical structure of Ni[sub n][sup +]. [ABSTRACT FROM AUTHOR]

Published
2001

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