A theoretical study on a novel cartesian product operator formalism applicable to strongly-coupled two-spin 1/2 systems in solution-state and solid-state MAS NMR spectroscopy

In solution-state and solid-state MAS (Magic Angle Spinning) NMR (Nuclear Magnetic Resonance) spectroscopy, a comprehensive product operator formalism applicable to general two-spin 1/2 systems, including strongly-coupled systems, is proposed. The formalism employs standard product operators, based on the orthogonal coordinate system, easily evaluating the effects of RF (Radio Frequency) pulse sequences. Solid-state anisotropic interactions modulated by MAS are treated in the perturbation theory, yielding striking solid-state effects, whereas the absence of those interactions leads to solution-state cases with strong couplings. Solid-state MAS INADEQUATE spectra are found to give rise to auto-correlation signals even for the spin pairs possessing an identical isotropic chemical shift. (author)