Formation of muonium substituted free radicals

SR experiments with mixtures of benzene with cyclohexane, 2,3-dimethyl-1,3-butadiene and carbontetrachloride allow the conclusion that the direct muonic precursor of the muonic cyclohexadienyl radical is thermal muonium. In neat benzene it has a life time of 10 ps and disappears by the addition reaction. Muonium is formed within about 1 ps by combination of the positive muon with an electron near the end of the track of the thermalizing muon.Support by the Swiss National Foundation for Scientific Research and by the Swiss Institute for Nuclear Research (SIN) are gratefully acknowledged.