Two-Dimensional Rotational Spin-Echo Nuclear Magnetic Resonance in Solids: Correlation of Chemical Shift and Dipolar Interactions

Two-dimensional NMR techniques which separate the chemical shift and heteronuclear dipolar interactions are applied to samples spinning at the magic angle. Because of the inhomogeneous nature of the two interactions, rotational echoes are observed in the time domain of each dimension. The corresponding Fourier transforms yield rotational sideband spectra which provide information on the principal values and relative orientations of the shift and dipolar tensors, and, from the latter, internuclear distances may be calculated. The techniques therefore provide a means for obtaining structural data, for example, ¹³C-¹H and ¹⁵N-¹H distances, in powder samples.