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We describe here a new solid-state nuclear-magnetic-resonance (NMR) experiment for correlating anisotropic and isotropic chemical shifts of inequivalent nuclei in powdered samples. Spectra are obtained by processing signals arising from a spinning sample, acquired in independent experiments as a function of the angle between the axis of macroscopic rotation and the external magnetic field. This is in contrast to previously proposed techniques, which were based on sudden mechanical ftippings or multiple-pulse sequences. We show that the time evolution of variable-angle-spinning signals is determined by a distribution relating the isotropic frequencies of the spins with their corresponding chemical shift anisotropies. Fourier transformation of these data therefore affords a twodimensional NMR spectrum, in which line shapes of isotropic and anisotropic interactions are correlated. Theoretical and experimental considerations involved in the extraction of this spectral information are discussed, and the technique is illustrated by an analysis of 13C NMR anisotropy in glycine, cysteine, and p-anisic acid.

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We describe the measurement of a component of the nonadiabatic transition probability in a two-level system that depends only on the path through parameter space followed by the Hamiltonian, and not on how fast the path is traversed [M. V. Berry, Proc. R. Soc. London 430, 405 {1990)j.We performed the measurement by sweeping a radio-frequency field through the Zeeman resonance of carbon-13 in a static magnetic field and measuring the transition probability P at the end of each sweep. We found that, for appropriately chosen radio-frequency sweep forms, a factor of P is independent of the duration of the sweep, in accordance with the theory of Berry.