FORMATION OF MUONIUM AND A MUONIC RADICAL IN FULLERENE

Three distinct electronic states were detected for positive muons (mu+) after implantation into a C60 powder sample. About 40% of the mu+ remained in the bare ("diamagnetic") state, essentially an interstitial charged point particle. The rest of the muons were found to thermalize predominantly in two muonium (Mu = mu+ e-) atomic species. A "vacuum" Mu state, with hyperfine coupling close to that of free Mu, most likely at the molecular center, and a muonic substituted radical, i.e. a hydrogen-like Mu addition to double bonds on the carbon rings. This opens up a rich subfield of fullerene spectroscopy using muons.