K Ito

Sophia University, Edo, Tōkyō, Japan

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Publications (772)1849.96 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We present in detail a theoretical model that provides absolute cross sections for simultaneous core-ionization core-excitation (K(-2)V ) and compare its predictions with experimental results obtained on the water molecule after photoionization by synchrotron radiation. Two resonances of different symmetries are assigned in the main K(-2)V peak and comparable contributions from monopolar (direct shake-up) and dipolar (conjugate shake-up) core-valence excitations are identified. The main peak is observed with a much greater width than the total experimental resolution. This broadening is the signature of nuclear dynamics.
    The Journal of chemical physics. 01/2015; 142(1):014307.
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    ABSTRACT: The formalism developed in the companion Paper I is used here for the interpretation of spectra obtained recently on the nitrogen molecule. Double core-hole ionization K(-2) and core ionization-core excitation K(-2)V processes have been observed by coincidence electron spectroscopy after ionization by synchrotron radiation at different photon energies. Theoretical and experimental cross sections reported on an absolute scale are in satisfactory agreement. The evolution with photon energy of the relative contribution of shake-up and conjugate shake-up processes is discussed. The first main resonance in the K(-2)V spectrum is assigned to a K(-2)π(∗) state mainly populated by the 1s→ lowest unoccupied molecular orbital dipolar excitation, as it is in the K(-1)V NEXAFS (Near-Edge X-ray Absorption Fine Structure) signals. Closer to the K(-2) threshold Rydberg resonances have been also identified, and among them a K(-2)σ(∗) resonance characterized by a large amount of 2s/2p hybridization, and double K(-2)(2σ(∗)/1π/3σ)(-1)1π(∗2) shake-up states. These resonances correspond in NEXAFS spectra to, respectively, the well-known σ(∗) shape resonance and double excitation K(-1)(2σ(∗)/1π/3σ)(-1)1π(∗2) resonances, all being positioned above the threshold.
    The Journal of chemical physics. 01/2015; 142(1):014308.
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    ABSTRACT: We have observed single photon one-site (K−2) and two-sites (K−1K−1) double K-shell ionization in C2H2n (n=1-3) sequence and in isoelectronic C2H2, N2 and CO molecules. The spectroscopy of K−1K−1 states is much more sensitive to the bond length than conventional ESCA spectroscopy based on single K-shell ionization. The mechanism of single photon two-sites is due to a knock-out process in which a primary photoionized 1s electrons eject another 1s electron on the neighbor atom.
    Journal of Physics Conference Series 04/2014; 488(2):022013.
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    ABSTRACT: Absolute total cross sections for electron scattering from He and Ne at electron energies ranging from 6 meV to 20 eV were obtained with the experimental technique employing the threshold-photoelectron source. The measured total cross sections were compared with previous experimental and theoretical cross sections.
    Journal of Physics Conference Series 04/2014; 488(4):042015.
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    ABSTRACT: We have studied double photoionization from molecular inner-shell orbitals and investigated the properties of the resultant double core-hole states in molecules, by multi-electron coincidence spectroscopy with a magnetic bottle electron spectrometer. A brief summary of our previous studies is presented.
    Journal of Physics Conference Series 04/2014; 488(1):012012.
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    ABSTRACT: A new experimental technique for the total cross section measurements of ultra-low energy electron collisions with atoms and molecules utilizing the synchrotron radiation is presented. The technique employs a combination of the penetrating field technique and the threshold photoionization of rare gas atoms using the synchrotron radiation as an electron source in order to produce a high resolution electron beam at very low energy. Absolute total cross sections for electron scattering from He, Ne, Ar, Kr, and Xe in the energy region from extremely low electron energy to 20 eV are presented.
    02/2014; 1588(1).
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    ABSTRACT: The multiple Auger electron emission processes after the 2p3/2-1 4s excitation in Ar have been investigated with a multielectron coincidence method. We have observed the double, triple, and quadruple Auger decays of the resonant state, where both cascade and direct processes are identified. The cascade processes in the resonant double and triple Auger decays result mostly from the spectator behavior of the Rydberg electron in the initial core-hole decay: First Auger decay produces ion states with large internal energies, and subsequent electron emission leads mainly formation of ground Ar2+ and Ar3+ states. It is revealed that spectator behavior, which is known to be the dominant path in resonant single Auger decay, is also important in the direct paths of the resonant double and triple Auger decays. In contrast, the participation of the Rydberg electron is predominant in the direct path of the resonant quadruple Auger decay.
    Physical Review A 01/2014; 89(2). · 2.99 Impact Factor
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    ABSTRACT: Absolute total cross sections for electron scattering from He and Ne are obtained in the energy range from 20 eV down to below 10 meV with a very narrow electron energy width of 6-8 meV using the threshold-photoelectron source. Total cross sections obtained in the present study generally agree well with those obtained in the previous experiments for both He and Ne above 100 meV, where several experimental works have been reported. Comparison of the present cross sections with the theoretical cross sections which have been regarded as the "standard" cross sections shows very good agreement even at very low energies below 10 meV, which confirms the validity of theoretical cross sections. The scattering lengths for electron scattering from He and Ne are also determined from the present total cross sections using the modified effective range theory. The resonant structures in the total cross sections due to Feshbach resonances of He and Ne are also observed. Analysis of the resonant structure was carried out based on the spin-dependent resonant scattering theory in order to determine the values of natural width of Feshbach resonance of Ne.
    Physical Review A 01/2014; 89(2). · 2.99 Impact Factor
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    ABSTRACT: The tabletop plasma trap experiment named "S-POD" is employed to explore the stability of intense charged-particle beams focused by a series of quadrupole doublet cells. S-POD is a compact linear Paul-trap, where we generate a single-species non-neutral ion plasma that can approximately reproduce the collective motion of an intense beam focused by periodic linear forces. Unlike conventional beam-dynamics experiments relying on large-scale transport channels and accelerators, it is straightforward in S-POD to control the functional form of quadrupole beam focusing over a wide range of variation to explore a variety of quadrupole focusing lattices. We systematically measure the loss rate of trapped particles as a function of bare betatron tune to locate resonance bands in which the plasma becomes unstable. It is confirmed that a few bands of coherent resonances appear depending on the beam intensity. When there is an imbalance between the horizontal and vertical focusing, those instability bands split. Experimental results indicate that the instability band is relatively insensitive to the phase of quadrupole focusing element placement within the doublet configuration over a significant range of parameters. Experimental observations are compared with transverse slice particle-in-cell simulations carried out using the Warp code.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2014; · 1.32 Impact Factor
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    ABSTRACT: An overview is given of the novel beam-dynamics experiments based on compact non-neutral plasma traps at Hiroshima University. We have designed and constructed two different classes of trap systems, one of which uses a radio-frequency electric field (Paul trap) and the other uses an axial magnetic field (Penning trap) for transverse plasma confinement. These systems are called "S-POD" (Simulator for Particle Orbit Dynamics). The S-POD systems can approximately reproduce the collective motion of a charged-particle beam propagating through long alternating-gradient (AG) quadrupole focusing channels using the Paul trap and long continuous focusing channels using the Penning trap. This allows us to study various beam-dynamics issues in compact and inexpensive experiments without relying on large-scale accelerators. So far, the linear Paul traps have been applied for the study of resonance-related issues including coherent-resonance-induced stop bands and their dependence on AG lattice structures, resonance crossing in fixed-field AG accelerators, ultralow-emittance beam stability, etc. The Penning trap with multi-ring electrodes has been employed primarily for the study of beam halo formation driven by initial distribution perturbations. In this paper, we briefly overview the S-POD systems, and then summarize recent experimental results on resonance effects and halo formation.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2014; · 1.32 Impact Factor
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    ABSTRACT: We have studied single photon double K-shell ionization of small molecules (N2, CO, C2H2n (n = 1–3), …) and the Auger decay of the resulting double core hole (DCH) molecular ions thanks to multi-electron coincidence spectroscopy using a magnetic bottle time-of-flight spectrometer. The relative cross-sections for single-site (K−2) and two-site (K−1K−1) double K-shell ionization with respect to single K-shell (K−1) ionization have been measured that gives important information on the mechanisms of single photon double ionization. The spectroscopy of two-site (K−1K−1) DCH states in the C2H2n (n = 1–3) series shows important chemical shifts due to a strong dependence on the C −2
    Journal of Electron Spectroscopy and Related Phenomena 10/2013; · 1.55 Impact Factor
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    ABSTRACT: Simultaneous core ionization and core excitation have been observed in the C_{2}H_{2n} (n=1, 2, 3) molecular series using synchrotron radiation and a magnetic bottle time-of-flight electron spectrometer. Rich satellite patterns corresponding to (K^{-2}V) core excited states of the K^{-1} molecular ions have been identified by detecting in coincidence the photoelectron with the two Auger electrons resulting from the double core hole relaxation. A theoretical model is proposed providing absolute photoionization cross sections and revealing clear signatures of direct (monopolar) and conjugate (dipolar near-edge x-ray absorption fine structure) shakeup lines of comparable magnitude.
    Physical Review Letters 09/2013; 111(12):123001. · 7.73 Impact Factor
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    ABSTRACT: Electron reemission following photoelectron recapture due to post-collision interaction has been studied at 0.7 eV the inner-shell photoionization threshold of water molecules, using a multi-electron coincidence method. Electron reemissions after single Auger decay occur from O and OH fragments which are produced by the dissociations of high-n Rydberg H2O(+) states populated through photoelectron recapture. In addition, electron reemissions after double Auger decay are identified in triple coincidence events, where autoionization lines from O and O(+) fragments are observed.
    The Journal of Chemical Physics 06/2013; 138(21):214308. · 3.12 Impact Factor
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    ABSTRACT: We have observed single photon double K-shell photoionization in the C_{2}H_{2n} (n=1-3) hydrocarbon sequence and in N_{2} and CO, using synchrotron radiation and electron coincidence spectroscopy. Our previous observations of the K^{-2} process in these molecules are extended by the observations of a single photon double photoionization with one core hole created at each of the two neighboring atoms in the molecule (K^{-1}K^{-1} process). In the C_{2}H_{2n} sequence, the spectroscopy of K^{-1}K^{-1} states is much more sensitive to the bond length than conventional electron spectroscopy for chemical analysis spectroscopy based on single K-shell ionization. The cross section variation for single photon K^{-1}K^{-1} double core ionization in the C_{2}H_{2n} sequence and in the isoelectronic C_{2}H_{2}, N_{2} and CO molecules validates a knock-out mechanism in which a primary ionized 1s photoelectron ejects another 1s electron of the neighbor atom. The specific Auger decay from such states is clearly observed in the CO case.
    Physical Review Letters 04/2013; 110(16):163001. · 7.73 Impact Factor
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    ABSTRACT: We have observed single photon double K-shell photoionization in the C2H2n (n=1–3) hydrocarbon sequence and in N2 and CO, using synchrotron radiation and electron coincidence spectroscopy. Our previous observations of the K-2 process in these molecules are extended by the observations of a single photon double photoionization with one core hole created at each of the two neighboring atoms in the molecule (K-1K-1 process). In the C2H2n sequence, the spectroscopy of K-1K-1 states is much more sensitive to the bond length than conventional electron spectroscopy for chemical analysis spectroscopy based on single K-shell ionization. The cross section variation for single photon K-1K-1 double core ionization in the C2H2n sequence and in the isoelectronic C2H2, N2 and CO molecules validates a knock-out mechanism in which a primary ionized 1s photoelectron ejects another 1s electron of the neighbor atom. The specific Auger decay from such states is clearly observed in the CO case.
    Physical Review Letters 04/2013; 110(16). · 7.73 Impact Factor
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    ABSTRACT: Direct measurements of the photoelectrons or Auger electrons associated with inner shell ionization of positively charged ions are extremely difficult and rarely realized. We propose an alternative method to simulate such measurements, based on core valence double photoionization of the neutral species. As an example, we obtain the spectroscopy, lifetimes, and Auger decays of the states arising from 2p inner shell ionisation of an Ar+ ion. Observations compare well with theoretical predictions obtained within multiconfigurational Dirac-Fock formalism.
    Physical Review Letters 03/2013; 110(11). · 7.73 Impact Factor
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    ABSTRACT: This paper reports on quantitative evaluation of influence of dopamine neurons on the flight locomotion of a fruit fly (Drosophila menanogaster). The aerodynamic force was measured by MEMS triaxial forcesensor. We compared the aerodynamic force of the genetically modified flies whose dopamine neurons (DDCII) are functionally blocked with that of the wild type ones. The peak aerodynamic force generated by wild type flies was controlled smoothly. By contrast, the peak aerodynamic force generated by genetically modified flies showed rough fluctuation. The Peak variability of the wild type flies and genetically modified flies were 0.06 ± 0.04 and 0.18 ± 0.14 [-] (Average ± S.D.), respectively. The result indicated that the DDCII-expressing dopamine neurons were necessary to control their flapping flight.
    2013 IEEE 26th International Conference on Micro Electro Mechanical Systems (MEMS); 01/2013
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    ABSTRACT: Double Auger decay of O1s(-1) and its satellite states in H(2)O has been studied with a multi-electron coincidence method, and a process leading to autoionizing O(∗) fragments has been revealed. The breaking of the two O-H bonds producing the autoionizing O(∗) fragments occurs for highly excited H(2)O(2+) populated by the initial Auger decay. The O(∗) fragments are more favorably produced in the decay from the satellite states, resulting from the larger population of highly excited H(2)O(2+) states inheriting the valence excitation in the initial state.
    The Journal of Chemical Physics 11/2012; 137(19):191101. · 3.12 Impact Factor
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    ABSTRACT: Total cross sections for electron scattering from Ar, Kr, Xe and N2 at electron energies ranging below thermal energy to 20 eV with high-energy resolution obtained are presented. A new experimental technique which employs a combination of the penetrating field technique and the threshold photoionization of rare gas atoms using the synchrotron radiation as an electron source in order to produce a high resolution electron beam at very low energy was developed for the measurements. The lowermost energy of the present measurement reaches to the cold electron collisions regime, where the de Broglie wavelength of an electron becomes much lager than the typical size of target.
    Journal of Physics Conference Series 11/2012; 388(4):2004-.
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    ABSTRACT: We observed an interference originating from coincidence detection of two indistinguishable electron pairs emitted upon photoionization of 4d electron in Xe. At 89.9 eV photon impact the energy of photoelectron ejected from 4d5/2 orbital equals energy of Auger electron emitted in decay of 4d3/2 hole into the [5s5p1P] state, and for the same final state the energy of the 4d3/2 photoelectron equals the Auger electron energy in decay of 4d5/2 hole. An angle-integrated coincidence yield as a function of photon energy is measured with the magnetic bottle time-of-flight spectrometer and shows a peak at the expected energy position.
    Journal of Physics Conference Series 11/2012; 388(2):2094-.

Publication Stats

11k Citations
1,849.96 Total Impact Points

Institutions

  • 2014
    • Sophia University
      • Department of Materials and Life Sciences
      Edo, Tōkyō, Japan
  • 1998–2014
    • Pierre and Marie Curie University - Paris 6
      • Laboratoire de Chimie Physique - Matière et Rayonnement (LCPMR)
      Lutetia Parisorum, Île-de-France, France
    • High Energy Accelerator Research Organization
      • Institute of Materials Structure Science
      Tsukuba, Ibaraki-ken, Japan
    • National Cerebral and Cardiovascular Center
      • Department of Cardiovascular Medicine
      Ōsaka, Ōsaka, Japan
    • Kumamoto University
      • Faculty of Education
      Kumamoto, Kumamoto Prefecture, Japan
  • 2013
    • Tokyo Institute of Technology
      • Chemistry Department
      Tokyo, Tokyo-to, Japan
  • 2011–2013
    • Niigata University
      • Department of Environmental Science
      Niahi-niigata, Niigata, Japan
  • 1994–2012
    • Nihon University
      • • Department of Periodontology
      • • Department of Endodontics
      • • Department of Pathology
      Edo, Tōkyō, Japan
    • Toyama University
      Тояма, Toyama, Japan
    • Shanghai Medical University
      Shanghai, Shanghai Shi, China
  • 1989–2012
    • Hiroshima University
      • • Graduate School of Advanced Sciences of Matter
      • • Department of Radiology
      Hirosima, Hiroshima, Japan
    • Kitasato University
      • Medical Department
      Edo, Tōkyō, Japan
  • 2010
    • Tokyo Medical and Dental University
      Edo, Tōkyō, Japan
  • 2009
    • Universiteit Utrecht
      • Utrecht Institute for Pharmaceutical Sciences
      Utrecht, Provincie Utrecht, Netherlands
  • 2004–2009
    • Imperial College London
      • Section of Airway Disease
      Londinium, England, United Kingdom
  • 2004–2007
    • Toho University
      • • Department of Pathology
      • • Department of Immunology
      Edo, Tōkyō, Japan
  • 1985–2007
    • Ito Hospital
      Edo, Tōkyō, Japan
    • French National Centre for Scientific Research
      Lutetia Parisorum, Île-de-France, France
  • 2005
    • University of Fukui
      • Division of Physics
      Hukui, Fukui, Japan
  • 2000–2005
    • Nippon Medical School
      • Department of Molecular Biology
      Tokyo, Tokyo-to, Japan
  • 1994–2004
    • Nagoya University
      • Division of Surgery
      Nagoya-shi, Aichi-ken, Japan
  • 2001–2003
    • National Heart, Lung, and Blood Institute
      Maryland, United States
    • Université Paris-Sud 11
      Orsay, Île-de-France, France
    • Showa University
      • Department of Medicine
      Shinagawa, Tōkyō, Japan
    • St. Marianna University School of Medicine
      • Department of Internal Medicine
      Japan
  • 1998–2002
    • Tohoku University
      • • Institute for Materials Research
      • • Institute of Multidisciplinary Research for Advanced Materials (IMRAM)
      Sendai, Kagoshima, Japan
    • University of Tsukuba
      • Applied Physics
      Tsukuba, Ibaraki-ken, Japan
  • 1984–2002
    • The University of Tokyo
      • • Faculty of Science and Graduate School of Science
      • • Department of Internal Medicine
      • • Faculty & Graduate School of Medicine
      • • School of Medicine
      Tokyo, Tokyo-to, Japan
  • 1999–2001
    • NGH Japan Co., Ltd.
      Edo, Tōkyō, Japan
    • Nakano Children's Hospital
      Ōsaka, Ōsaka, Japan
  • 1998–2001
    • Kokura Memorial Hospital
      Kitakyūshū, Fukuoka, Japan
  • 1998–1999
    • The Jikei University School of Medicine
      • Department of Internal Medicine H
      Tokyo, Tokyo-to, Japan
  • 1988–1999
    • Kyoto University
      • • Department of Materials Science and Engineering
      • • Division of Environmental Science and Technology
      • • Department of Polymer Chemistry
      Kioto, Kyōto, Japan
  • 1993–1998
    • Nagasaki University Hospital
      Nagasaki, Nagasaki, Japan
    • Tokyo Metropolitan Komagome Hospital
      Edo, Tōkyō, Japan
  • 1990–1998
    • Tokai University
      • • School of Medicine
      • • Department of Physiology
      • • Department of Pathology
      Hiratuka, Kanagawa, Japan
    • Hyogo College of Medicine
      • Department of Internal Medicine
      Nishinomiya, Hyogo-ken, Japan
  • 1995
    • Aichi Medical University
      • Department of Pathology
      Okazaki, Aichi, Japan
    • Ja Hiroshima General Hospital
      Hirosima, Hiroshima, Japan
    • AJINOMOTO CO., INC.
      Edo, Tōkyō, Japan
  • 1989–1995
    • Teikyo University Hospital
      Edo, Tōkyō, Japan
  • 1992–1994
    • Saitama Medical University
      • Department of Internal Medicine
      Saitama, Saitama-ken, Japan
    • Nagoya Institute of Technology
      • Faculty of Engineering
      Nagoya, Aichi, Japan
  • 1990–1992
    • Kochi Medical School
      Kôti, Kōchi, Japan
  • 1991
    • Hiroshima City Hospital
      Hirosima, Hiroshima, Japan