Free radicals formed by H(Mu) addition to pyrene

Muonium addition to pyrene has been investigated by means of transverse fie ld muon spin rotation and muon level-crossing spectroscopy. Two hydropyreny l radicals are produced and easily detected while a third is formed in low abundance. Muon and proton hyperfine constants were experimentally determin ed and compared with semiempirical and ab initio calculations. It is conclu ded that the radicals are of cyclohexadienyl type, i.e., the Mu adds only t o carbon atoms that can assume a tetrahedral -CHMu- configuration without d istorting the planar carbon skeleton of pyrene.