Muonium

A muonium particle is an exotic atom made up of a positive muon and an electron, and is given the symbol Mu or μ⁺e^–. During the muon's 2 microsecond lifetime, muonium can enter into compounds such as muonium chloride (MuCl) or sodium muonide (NaMu) [1] (http://www.iupac.org/publications/pac/2001/pdf/7302x0377.pdf).

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