Towards high-resolution NMR of more nuclei in solids: Sample spinning with time-dependent spinner axis angle

Heteronuclear spin decoupling in solid-state NMR under magic-angle sample spinning

“…Only the second-rank tensor contribution is averaged out by 11 the MAS rotation. However, by using different spatial averaging techniques such as dynamic-angle spinning (DAS) or double rotation (DOR) (32), (33), (34) it would be possible to average out both the second-rank and the fourth-rank parts of the cross term simultaneously, leaving only the isotropic (zeroth-rank tensor) part unchanged.…”

Scalar operators in solid-state NMR

“…These approaches are called dynamic angle spinning (DAS) [73,76] and double rotation (DOR) [72,104,78].…”

“…3.8 or 3.20), and thus cannot be removed completely by the conventional magic angle spinning (MAS) method [56,58] (see Figure 3.4). Recently, it has been proven experimentally that double rotation (DOR) [72,78,104] as well as dynamical angle spinning (DAS) [76,73] are the right solutions to suppress the second-order anisotropic broadening and yield high resolution spectra. In DOR, a small inner rotor is embedded in a large outer rotor (see …”

Slow turning reveals enormous quadrupolar interactions (STREAQI)

“…Narita et al [1] and Baugher et al [2] showed how the singularities of the second-order quadrupole perturbed central transition spectra could be used to determine the principal values of the quadrupole coupling tensor, and Kundla et al [3] computed how these powder patterns are narrowed but not eliminated under magic angle spinning. The advent of double rotation [4] and [5] dynamic angle spinning [5] and [6], MQMAS [7], and STMAS [8] has provided a toolbox of useful experiments for narrowing these resonances to isotropic lines, and opened up a number of useful applications of highresolution solid-state NMR of quadrupolar nuclei for the study of minerals, glasses, and other systems.…”

“…Possible methods for changing the angles θ and φ include a discontinuous jump between two orientations, such has been used in dynamic-angle spinning [5] and [6] and magic-angle hopping [10]; a fi eld jump, implemented electronically; or slow continuous sample rotation over an extended interval, as has been implemented in the magic-angle turning experiment [11] and extensions of it [12]. We have adopted the last method, largely for practical reasons: slow rotation is readily achieved using a magic-angle spinning probe; it can be carefully and precisely controlled without the wear-and-tear that results from fast, discrete jumps, and does not require shifting the direction of large magnetic fi elds.…”