A new muonium centre, Mux, with an anisotropic hyperfine interaction was discovered in crystalline material during transverse-field muon spin rotation experiments. Its hyperfine tensor was very close to that of bond-centered muonium, MuBC. The new muonium centre was observed in only some of the many samples which were investigated. A correlation was found between dopant and O concentrations in the investigated samples, and the observation of Mux. This suggested that Mux might be related to an O-muonium centre. According to the hyperfine tensor of Mux, the new muonium species was attributed to an O-MuBC complex. The Mux signal was affected by applied electrostatic fields; unlike the signal of any other known muon species.

Oxygen-Related Anisotropic Muonium Centres in Crystalline Silicon M.Schefzik, R.Scheuermann, L.Schimmele, A.Seeger, D.Herlach, O.Kormann, J.Major, A.Röck: Philosophical Magazine B, 1999, 79[10], 1561-75