Muonium

Onia Muonium (/mjuːˈoʊniəm/) is an exotic atom made up of an antimuon and an electron,[1] which was discovered in 1960 by Vernon W. Hughes[2] and is given the chemical symbol Mu.

[3] Because, like a proton, the antimuon's mass is vastly larger than that of the electron, muonium (μ+e−) is more similar to atomic hydrogen (p+e−) than positronium (e+e−).

Like ESR, μSR is useful for the analysis of chemical transformations and the structure of compounds with novel or potentially valuable electronic properties.

Because the muon is a lepton, the atomic energy levels of muonium can be calculated with great precision from quantum electrodynamics (QED), unlike in the case of hydrogen, where the precision is limited by uncertainties related to the internal structure of the proton.

For this reason, muonium is an ideal system for studying bound-state QED and also for searching for physics beyond the Standard Model.