Laser Spectroscopy Measurements of Metastable Pionic Helium Atoms at Paul Scherrer Institute

Few Body Syst. 2021;62(3):63. doi: 10.1007/s00601-021-01630-3. Epub 2021 Jul 29.

Abstract

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.