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Ryuichi Arafune

Independent Scientist

Affiliation:

  • MANA, NIMS
    • Specialty:

      • Surface/Interface Dynamics, Electron Spectroscopy
        • Academic degree:


Educational & Research History

2010 Apr - Present
Independent Scientist, MANA, NIMS
2006 Oct - 2010 Mar
Researcher, JST Project, PRESTO "Structure Function and Measurement Analysis"
2005 Nov - 2006 Oct
Postdoctoral Researcher, Graduate school of Frontier Sciences, University of Tokyo
2001 - 2005 Oct
Postdoctoral Researcher, Surface Photodynamics, RIKEN Photodynamics Research Center
1998 - 2001
Postdoctoral Researcher, Ushioda Group, JST

Research Accomplishments

Molecular orientational correlation between liquid crystals and rubbed polyimide films (1993~1998)
STM light emission spectroscopy for molecular covered metal surfaces. (1998~2001)
Laser photoemission spectroscopy (2001~)

We succeeded in detecting the energy loss of photoelectrons by scattering from vibrational modes of the adsorbed molecule by measuring the photoemission spectra excited by the low energy laser light. Generally, very-low-energy electrons at the surface have a long time for interacting with surface vibrational excitations, such as surface phonons and surface adsorbate vibrations. Thus, one would expect that the high-resolution low energy photoemission spectra contain information about surface vibrational excitations. To measure the spectra of the low energy photoelectron with high resolution, a laser was used as the low energy excitation light source. A clear step appears at 34.6 meV below the Fermi level in the laser photoemission spectrum of the CO covered Cu(001). This energy agrees with the vibrational energy of the frustrated rotation mode.

In addition, we observed the step structure originating from phonons as well. An energy gain process (anti-stokes process) also has been found in laser photoemission process. These results manifest that laser photoemission spectroscopy can be used as a novel vibrational spectroscopic tool for molecular adsorbed surfaces. Originality: Although conceptually simple, this inelastic interaction during the photoemission process had not been observed thus far. We demonstrated another facet of the laser photoemission spectroscopy, the investigation of the vibrational dynamics at the solid surfaces.



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Future Objectives

  • Development of novel laser photoemission spectroscopic method and its application to molecular systems
Backgrounds and Specific Aims:
The aim of this research project is the development of a novel photoemission spectroscopy (PES) and measurement of the vibrational dynamics at solid surfaces and interfaces. By measuring low energy photoelectron spectra of surfaces excited by the pulse laser light whose energy is tuned slightly higher than the work function of the solid surface, we will elucidate some aspects of the dynamic interactions between low-energy electrons and surface elementary excitations. This technique enables us to investigate vibrational and electronic dynamics of adsorbates on solid surfaces in the time range of picoseconds to femtoseconds.


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Awards


Selected Papers

  1. Mechanism of vibrational excitation in inelastic photoemission from solid surfaces
    Arafune R, Yamamoto MQ, Takagi N, Kawai M
    Phys Rev B Condens Matter Mater Phys, 2009; 80(7): 073407.
  2. 光電子の非弾性放出現象を利用した表面・界面振動プローブ (in Japanese)
    Arafune R
    J Vac Soc Jpn, 2008; 51(6): 364-367.
  3. Spectroscopic evidence for energy loss of photoelectrons interacting with image charge
    Arafune R, Hayashi K, Ueda S, Uehara Y, Ushioda S
    J Physical Soc Japan, 2007; 76(4): 044604.
  4. Vibrationally Induced Inelastic Structures in Laser Photoemission Spectra (in Japanese)
    Arafune R, Hayashi K, Takagi N, Kawai N, Uehara Y, Ushioda S
    表面科学, 2007; 28(7): 378-384.
  5. Derivative spectra of very low energy photoelectrons from CO/Cu(001) surface obtained by a lock-in technique
    Hayashi K, Arafune R, Ueda S, Uehara Y, Ushioda S
    J Physical Soc Japan, 2006; 75: 104303.
  6. Detection of the frustrated rotation mode of CO on Cu(001) by very low energy photoelectron spectroscopy
    Arafune R, Hayashi K, Ueda S, Uehara Y, Ushioda S
    Surf Sci, 2006; 600(18): 3536-3539.
  7. 超低速光電子分光による放出光電子のエネルギー損失観測 (in Japanese)
    Arafune R, Hayashi K, Ueda S, Uehara Y, Ushioda S
    表面科学, 2005; 26(12): 741-745.
  8. Dynamics of very low energy photoelectron interacting with image charge of Cs/Cu(111) surface
    Hayashi K, Arafune R, Ueda S, Uehara Y, Ushioda S
    Phys Rev B Condens Matter Mater Phys, 2005; 72(19): 195425.
  9. Inelastic photoemission due to scattering by surface adsorbate vibrations
    Arafune R, Hayashi K, Ueda S, Uehara Y, Ushioda S
    Phys Rev Lett, 2005; 95(20): 207601.
  10. Energy loss of photoelectrons by interaction with image charge
    Arafune R, Hayashi K, Ueda S, Ushioda S
    Phys Rev Lett, 2004; 92(24): 247601.
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