TEMPERATURE-DEPENDENCE OF THE MUON AND PROTON HYPERFINE CONSTANTS OF AN ALPHA-MUONIUM-SUBSTITUTED METHYL RADICAL

Muon hyperfine constants A, have been measured by transverse field mu SR for (CH3)(3)SiCHMu in hexane from 167 K to 332 K. In addition, avoi ded level-crossing resonance was used to determine alpha-proton coupli ng constants A(p) over a similar range of temperatures. The two hyperf ine constants can be described by a common temperature dependence, d\A (i)\/dT = 1.4 x 10(-3) MHzK(-1), where A(i) represents A(p) or the red uced muon constant A(mu)' = 0.3141A(mu). There is a small isotope effe ct (A(mu)' is 2.2 % larger than A(p)) consistent with zero-point motio n in the anharmonic C-H bond stretch. The common temperature dependenc e is tentatively attributed to a coupled deviation of the C-H and C-Mu bonds out of the nodal plane of the p orbital containing the unpaired electron.