Multiple-quantum NMR in anisotropic phases: Projections of two-dimensional MQNMR spectra

The use of two-dimensional transform techniques in the observation of multiple-quantum transitions in large spin systems in anisotropic environments is described. In the case of partial resolution in the ω₂ dimension, it is shown that the signal to noise of the projection onto ω₁ of the absolute magnitude two-dimensional multiple-quantum spectrum is considerably greater than that of the Fourier transform of the t₂ = 0 cross section. In practical terms, multiple- quantum transitions of very high order may be observed with good signal to noise after acquisition periods much shorter than previously reported by cross section methods.