Intrinsic asymmetry in multidimensional solid-state NMR correlation spectra

Solid-state MAS correlation spectra involving cross polarization will generally provide spectra which are asymmetric about the main diagonal. A quantitative treatment of this effect is provided and is demonstrated experimentally with examples of two-dimensional spin-diffusion spectra, The effect, which is due to the nonuniform nonequilibrium initial coherent state induced by cross polarization, is usually pronounced, and cannot be eliminated simply. It must be taken into account when quantifying solid-state CPMAS correlation spectra. (C) 1998 Academic Press.