Wigner function techniques

A major recent advance in the study of quadrupolar nuclei by solid-state NMR is the development of double-rotation (DOR) and dynamic-angle spinning (DAS) [ 158,159,163). These techniques are capable of removing not only the first-order effects such as chemical shift anisotropy, but also the second-order quadrupolar interaction, which, as we have seen above, affects all quadrupolar nuclei. The second-order interaction can be expanded as a function of Wigner rotation matrices D " , so that the shift of the central transition is... 

Abstract The partitioning technique is described in some detail. The concept of a model space is introduced and the wave operator and the reaction operator are defined. Using these ideas, both the Rayleigh-Schrodinger and the Brillouin-Wigner expansions are developed, first for the case of a single-reference function and then for the multi-reference case. 

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