新たな原子系「多価ミュオンイオン」の観測に成功～宇宙観測検出器が捉えるエキゾチック原子の世界～

2025-05-19 東京都立大学

図１：本研究で観測した多価ミュオンイオン（μAr¹⁶⁺, μAr¹⁵⁺, μAr¹⁴⁺）の模式図。μAr¹⁶⁺, μAr¹⁵⁺, μAr¹⁴⁺は、負ミュオンに加えて電子をそれぞれ１, 2または3個束縛している。

＜関連情報＞

• https://www.tmu.ac.jp/news/topics/37784.html
• https://www.tmu.ac.jp/extra/download.html?d=assets/files/download/news/press/20250619_tmupress.pdf
• https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.134.243001

電子顕微鏡で検証された少数電子高電荷ミュオンAr原子X線 Few-Electron Highly Charged Muonic Ar Atoms Verified by Electronic X Rays

T. Okumura, T. Azuma, D. A. Bennett, W. B. Doriese, M. S. Durkin, J. W. Fowler, J. D. Gard, T. Hashimoto, R. Hayakawa et al.
Physical Review Letters  Published: 16 June, 2025
DOI: https://doi.org/10.1103/PhysRevLett.134.243001

Abstract

A highly charged muonic ion is a unique few-body atomic system where a negatively charged muon and a few electrons are simultaneously bound to a single nucleus. We report the first state-selective observation of highly charged muonic Ar (⁢Ar) by electronic x-ray spectroscopy using an array of transition-edge sensor microcalorimeters. The high-precision x-ray spectra provide a clear signature of the presence of muonic atoms with one, two, and three electrons, i.e., H-like, He-like, and Li-like ⁢Ar. With the aid of theoretical calculations, we confirmed that the peak positions are consistent with the x-ray energies from highly charged Cl ions, and the intensities reflect deexcitation dynamics of highly charged ⁢Ar.