Multistep Ionization of Ar Atoms by Extreme-Ultraviolet Free Electron Laser (Press Release)
- Release Date
- 24 Sep, 2010
- scss
Institute for Molecular Science
Niigata University
Nagoya University
RIKEN
Japan Synchrotron Radiation Research Institute
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A joint research team has successfully clarified details of the multielectron emission process by irradiating an intense extreme-ultraviolet free electron laser on Ar atoms. This was achieved by a joint research team consisting of two groups: one group consisted of Eiji Shigemasa, an associate professor at the Institute for Molecular Science, National Institutes of Natural Sciences, Yasumasa Hikosaka, an associate professor at the Faculty of Science, Niigata University, and Akiyoshi Hishikawa, a professor at the Department of Chemistry, Graduate School of Science, Nagoya University; the other group was a joint research group at the head office of the SPring-8 Joint Project for the X-ray Free Electron Laser (XFEL)*1 established by RIKEN and the Japanese Synchrotron Radiation Research Institute (JASRI). Scientists of the two groups analyzed the energy of all electrons emitted from laser pulses that were repeatedly irradiated onto Ar atoms at a rate of 20 pulses per second. The analytical results were used to accurately measure the fluctuation in the free electron laser light. They monitored the electrons associated with the absorption of multiple photons,*2 which only occurs when the light intensity is high, and clarified the significance of the resonant state*3 in the multiphoton absorption process. The achievements of this research suggest that appropriate resonance conditions based on the selection of a suitable laser wavelength can contribute to research on nanoscience, nanotechnology, and material fabrication using XFELs. The achievements of this research were published online in Physical Review Letters, the scientific journal of the American Physical Society, on 24 September 2010. Publication: |
<Figure>
Fig. 1 Magnetic-bottle-type photoelectron spectrometer
Fig. 2 Role of resonant state in two-electron emission induced by three-photon absorption
<Glossary>
*1 X-ray free electron laser (XFEL)
An XFEL is a laser with a wavelength in the X-ray region. Such lasers enable us to observe the atomic structures and ultrafast dynamics of various materials. Unlike conventional lasers, XFELs use free electrons, which are not bound to materials. In Japan's XFEL project, which is being promoted by RIKEN with the cooperation of JASRI, it is aimed that X-rays with a 1010 -fold higher brilliance and a 103 -fold shorter pulse width than those of the X-rays at SPring-8, the world’s highest-performance synchrotron radiation facility, will be publicly available from 2011. Japan’s XFEL is expected to contribute to innovative achievements in fundamental research, applied research useful for industry and in daily life, and developmental research ahead of XFELs in other countries.
*2 Photons
Light is considered to consist of photons when it is discussed in terms of the particle properties of electromagnetic waves. Photons are particles with an energy quantum of hνwhere ν is the frequency of electromagnetic waves and h is Planck’s constant. In the light absorption process, single photons are generally absorbed; however, multiple photons can be simultaneously absorbed when electromagnetic waves with a high photon density such as lasers are used. This phenomenon is called multiphoton absorption. Recently, applied research on multiphoton absorption using a Ti:sapphire laser has been intensively carried out, and multiphoton absorption techniques are widely applied to microscopes and nanofabrication technologies to obtain high three-dimensional resolution exceeding the diffraction limit.
*3 Resonant state
When an electron in a certain state undergoes a transition to a higher-energy state upon light absorption, an electromagnetic wave with a photon energy corresponding to the energy difference between the two states is selectively absorbed. The change in the electron state due to the absorption of intense light is called resonant excitation. The generated state with a high energy is called the resonant (excited) state. The level of light absorption markedly decreases when the energy of the electromagnetic wave deviates from the resonant excitation energy.
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For more information, please contact: Associate prof. Yasumasa Hikosaka (Niigata University) Prof. Akiyoshi Hishikawa (Nagoya University) Dr. Mitsuru Nagasono (RIKEN) Dr. Haruhiko Ohashi (JASRI) |
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