https://doi.org/10.1140/epjp/s13360-022-03229-x
Regular Article
K-x-ray emission of 1.5–20 keV/q Oq+ (q = 3, 5, 6) and Nq+ (q = 3, 5) ions impinging on nickel surface
1
Institute of Modern Physics, Chinese Academy of Sciences, 730000, Lanzhou, China
2
School of Nuclear Science and Technology, University of South China, 421001, Hengyang, China
3
School of Nuclear Science and Technology, Lanzhou University, 730000, Lanzhou, China
4
School of Nuclear Science and Technology, University of Chinese Academy of Sciences, 100049, Beijing, China
Received:
30
June
2022
Accepted:
24
August
2022
Published online:
7
September
2022
The spectra emitted by highly charged ions, which are abundant in laboratory plasma and stellar systems, cover a wide range of wavelengths from near-infrared to x-rays. Measurements on such spectral lines can provide plasma information such as the electron temperature, electron/ion density, chemical composition, and the evolution of these parameters. To simulate the x-ray emission from comets and other celestial bodies irradiated by solar wind ions in the laboratory, we established an experimental platform for x-ray measurements at Institute of Modern Physics, Chinese Academy of Sciences, and measured the x-ray emission spectra from a series of metal and silicate minerals bombarded by slow highly charged nitrogen and oxygen ions. In this paper, we describe the x-ray measurement platform in detail and report the x-ray emission caused by the interaction of 1.5–20 keV/q Oq+ (q = 3, 5, 6) and Nq+ (q = 3, 5) ions with nickel surface. It is discovered that the measured x-ray yield and production cross section increase rapidly as increasing the impact energy, but have no discernible dependence on the charge state of incident ions. The experimental results reveal that the incident ions have been neutralized and achieved charge state equilibration before the K-shell electron is ionized. When the incident energy is greater than 5 keV/q, the Binary Encounter Approximation calculations are consistent well with the experimental data, indicating that the K-shell ionization of incident ions is due to direct Coulomb excitation processes that occur below the target surface. However, the experimental ionization cross sections clearly deviate from the Binary Encounter Approximation calculations when the impact energy is less than 5 keV/q. The discrepancy at the low collision energy is discussed and explained based on a multi-electron excitation model.
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© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2022. Springer Nature or its licensor holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
