1) Exotic atom 
Muonium is an exotic atom made up of an antimuon and an electron, which was discovered in 1960 and is given the chemical symbol {Element2|Muonium}. During the muon`s {val|2.2|u=µs} lifetime, muonium can enter into compounds such as muonium chloride ({Element2|Muonium}{Element2|Chlorine}) or sodium muonide ({Element2|Sodium}{Element2|Muonium}). D....
positively-charged muon attached to an electron
short-lived quasi-atom composed of a positive muon (an antiparticle), as nucleus, and an ordinary negative electron. It is formed when a positive ... [1 related articles]
A short-lived entity formed by a muon and its antiparticle attracted together and revolving about a common center.
an electron and a positively charged muon bound together by electrical attraction in the same manner as the electron and proton in a hydrogen atom.