Tunneling spectroscopy from magnetization evolution in a tilted rotating frame of nuclear spins

The time evolution of the proton Zeeman magnetization in the rotating frame at the magic angle theta(M) = cos(-1)(1/root 3) is calculated for an isola ted tunneling methyl group and its Fourier transform is given. The calculat ion compares well with the experimental spectra of CH3CD2I and methylmaloni c acid. It is shown that Fourier transform spectroscopy of the magnetizatio n evolution in a tilted RF frame represents an excellent alternative to the analogous experiment performed at exact resonance, resulting in improved r esolution and a much better signal-to-noise ratio. (C) 2000 Academic Press.