We review recent experiments carried out by the PiHe collaboration of the Paul Scherrer Institute (PSI) that observed an infrared transition of three-body pionic helium atoms by laser spectroscopy. These measurements may lead to a precise determination of the charged pion mass, and complement experiments of antiprotonic helium atoms carried out at the new ELENA facility of CERN.

中文翻译：

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Paul Scherrer 研究所亚稳态 Pionic 氦原子的激光光谱测量

我们回顾了 Paul Scherrer 研究所 (PSI) 的 PiHe 合作最近进行的实验，该实验通过激光光谱观察了三体 pionic 氦原子的红外跃迁。这些测量可能导致带电π介子质量的精确测定，并补充在欧洲核子研究中心新的 ELENA 设施中进行的反质子氦原子实验。