Resolved nuclear hyperfine structure of a muonated free radical using level-crossing spectroscopy

The hyperfine (hf) couplings of all the ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ nuclei in the muonated free radical⋅${\mathrm{C}}_6$ ${\mathrm{F}}_6$-Mu have been measured using a level-crossing-resonance technique. Slow damped oscillations of the muon spin polarization in a large longitudinal magnetic field or frequency splittings in transverse field occur at particular field values at which there is a near degeneracy in the muon fluorine hf levels. Thus a resonantlike effect is observed in the muon-spin-rotation spectrum as a function of magnetic field. The positions of such level-crossing resonances allow an accurate determination of the magnitude and sign of the fluorine hf parameters relative to the muon hf parameter.