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RIKEN SPring-8 Center Theory Team

Team Leader: Kenji Tamasaku (D.Eng.)

Research Summary

Kenji  Tamasaku(D.Eng.)

SACLA offers extensive researches of optical science beyond conventional scientific research fields of biology, chemistry and physics. One purpose of our team is to investigate and explore new optical phenomena related to XFEL. Another purpose is to support analysis of pioneering experiments performed by SACLA. Our research is based on x-ray optics, nonlinear optics and condensed matter physics. However, we are collaborating with both theorists and experimentalists over research fields such as elementary particle physics, x-ray optics, condensed matter physics and microwave engineering. Such intense collaboration between theory and experiment triggers implication for next theoretical investigation that becomes feedback to another experiment.

Main Research Fields

  • Interdisciplinary Science & Engineering

Related Research Fields

  • Mathematical & Physical Sciences


  • X-ray optics
  • Nonlinear optics

Selected Publications

  • 1.K. Tamasaku, M. Taguchi, I. Inoue, T. Osaka, Y. Inubushi, M. Yabashi, and T. Ishikawa:
    “Two-dimensional Kβ-Kα fluorescence spectrum by nonlinear resonant inelastic X-ray scattering”
    Nature Communications 14, 4262 (2023).
  • 1.T. Masuda, A. Yoshimi, A. Fujieda, H. Fujimoto, H. Haba, H. Hara, T. Hiraki, H. Kaino, Y. Kasamatsu, S. Kitao, K. Konashi, Y. Miyamoto, K. Okai, S. Okubo, N. Sasao, M. Seto, T. Schumm, Y. Shigekawa, K. Suzuki, S. Stellmer, K. Tamasaku, S. Uetake, M. Watanabe, T. Watanabe, Y. Yasuda, A. Yamaguchi, Y. Yoda, T. Yokokita, M. Yoshimura, and K. Yoshimura:
    “X-ray pumping of the 229Th nuclear clock isomer”
    Nature 573, 238 (2019).
  • 1.K. Tamasaku, E. Shigemasa, Y. Inubushi, I. Inoue, T. Osaka, T. Katayama, M. Yabashi, A. Koide, T. Yokoyama, and T. Ishikawa:
    “Nonlinear Spectroscopy with X-ray Two-Photon Absorption in Metallic Copper”
    Physical Review Letters 121, 083901 (2018).
  • 1.T. Inada, T. Yamazaki, T. Namba, S. Asai, T. Kobayashi, K. Tamasaku, Y. Tanaka, Y. Inubushi, K. Sawada, M. Yabashi, T. Ishikawa, A. Matsuno, K. Kawaguchi, K. Kindo, and H. Nojiri:
    "Search for Two-Photon Interaction with Axionlike Particles Using High-Repetition Pulsed Magnets and Synchrotron X Rays"
    Physical Review Letters 118, 071803 (2017).
  • 1.K. Tamasaku, E. Shigemasa, Y. Inubushi, T. Katayama, K. Sawada, H. Yumoto, H. Ohashi, H. Mimura, M. Yabashi, K. Yamauchi, and T. Ishikawa:
    "X-ray two-photon absorption competing against single and sequential multiphoton processes"
    Nature Photonics 8, 313 (2014).
  • 1.T. Inada, T. Namba, S. Asai, T. Kobayashi, Y. Tanaka, K. Tamasaku, K. Sawada and T. Ishikawa:
    "Results of a Search for Paraphotons with Intense X-ray Beams at SPring-8"
    Physics Letters B 722, 301 (2013).
  • 1.Y. Kohmura, K. Sawada, S. Fukatsu and T. Ishikawa:
    "Controlling the Propagation of X-ray Waves inside a Heteroepitaxial Crystal Containing Quantum Dots Using Berry's Phase"
    Physical Review Letters 110, 057402 (2013).
  • 1.S. Tomita, Y. Kosaka, H. Yanagi and K. Sawada:
    "Chiral meta-interface; Polarity reversal of ellipticity through double layers consisting of transparent chiral and absorptive achiral media"
    Physical Review B 87, 041404(R) (2012).
  • 1.M. Kobayashi, S. Tomita, K. Sawada, K. Shiba, H. Yanagi, I. Yamashita and Y. Uraoka:
    "Chiral meta-molecules consisting of gold nanoparticles and genetically engineered tobacco mosaic virus"
    Optics Express 20, 24856 (2012).
  • 1.K. Tamasaku, K. Sawada, E. Nishibori and T. Ishikawa:
    "Visualizing the local optical response to extreme-ultraviolet radiation with a resolution of λ/380"
    Nature Physics 7, 705 (2011).

Recent Research Results

Related Links

Lab Members

Principal investigator

Kenji Tamasaku
Team Leader

Core members

Kei Sawada
Research Scientist


Position Deadline
Seeking a few Research Scientists or Postdoctoral Researchers (C22-0103) Open until filled

Contact Information

1-1-1 Kouto, Sayo-cho
Sayo-gun, Hyogo
679-5148 Japan
Email: tamasaku [at] spring8.or.jp