short-lived quasi-atom composed of a positive muon (an antiparticle), as nucleus, and an ordinary negative electron. It is formed when a positive muon captures an atomic electron after being slowed down in matter. Muoniums form a few compounds with gases such as nitrogen dioxide and ethylene. Muonium research throws some light on the puzzling nature of muons (essentially heavy electrons) and their relation to ordinary electrons.
Learn more about muonium with a free trial on Britannica.com.
|a chattering or flighty, light-headed person.|
|a fool or simpleton; ninny.|