Two-dimensional Zeeman polarization spectroscopy of tunneling atomic groups in solids

A spectral line at the rotational tunneling frequency omega(T), due to nonm agnetic transitions within the ground state manifold of a tunneling atomic group, has been observed in the Fourier spectrum of Zeeman polarization evo lution in the rotating frame of proton spins. These observations suggest a new 2D NMR method. We propose that the underlying conditions which make the nonmagnetic omega(T) peak observable in NMR experiments are quite general and are related to the properties of dipolar interaction under spin rotatio ns. [S0031-9007(99)08732-3].