Muonium is a hydrogen-like exotic atom , the nucleus of which is the positive muon μ + . The electron cloud of muonium consists of one electron . The reduced mass of muonium and its radius of the first Bohr orbit are close to the corresponding values for the hydrogen atom . Therefore, chemically, muonium behaves like atomic hydrogen and can be regarded as its ultra-light isotope ; However , the lifetime of this atom is very small (the muon is unstable and decays on average in 2.2 μs). The chemical symbol is Mu. Although the muon lifetime is short, muonium manages to form chemical compounds, such as muonium chloride (MuCl) and sodium muonide (NaMu). Muonium is formed when a positive muon is inhibited and stops in a substance, capturing an electron from the environment. Muonium should be distinguished from muon atoms, which arise when a negative atom is captured by a normal atom into an electron orbit.
- WH Koppenol ( IUPAC ). Names for muonium and hydrogen ions and ions (English) // : en: Pure and Applied Chemistry | Pure and Applied Chemistry : journal. - 2001. - Vol. 73 , no. 2 - P. 377-380 .