Intramolecular motion in the tert-butyl radical as studied by muon spin rotation and level-crossing spectroscopy

Muon spin rotation and muon level-crossing spectroscopy have been used to determine muon (Aμ) and proton (Ap) hyperfine coupling constants for the muon-substituted tert-butyl radical (CH3)2CCH2Mu over a wide range of temperature in isobutene. Ap(CH3) is almost constant, but Aμ(CH2Mu) falls and Ap(CH2Mu) rises with increasing temperature, consistent with a preferred conformation of the methyl group in which the CMu bond is coplanar with the …