Rotor-synchronized acquisition of quadrupolar satellite-transition NMR spectra: practical aspects and double-quantum filtration

Two-dimensional one pulse MAS of half-integer quadrupolar nuclei

“…Contributions from the satellite transitions in the N = 0 cross section are generally weaker, although they are higher for the AlO 6 site, due to its small quadrupolar coupling, and thus care should be taken if a quantitative analysis of the spectrum is performed [14]. The full projection, equivalent to the synchronous acquisition spectrum [15] shows all the transitions, and the projection over cross-sections with N = 0 contains only the satellite transitions (minus the intensity of the N = 0 band). Note that the full projection has a substantially lower signal-to-noise ratio than the N = 0 cross-section.…”

Spectral editing in solid-state MAS NMR of quadrupolar nuclei using selective satellite inversion

“…For spin I = 5/2 the inner satellite pair is significantly narrower, whereas for spins I = 7/2 and 9/2 it is the 2nd inner satellite pair, ±5/2, ±3/2 that is narrowest. This well-known narrowing [17][18][19][20][21][22], can be readily exploited with adiabatic inversion pulses to perform spectral editing of the central transition region. Thus, our approach is to use a (π/2) CT -(π) ST 1 -(π/2) CT sequence, where the central transition of all sites are pre-saturated by a (π/2) CT pulse, followed by restoration of the desired site's central transition polarization by selective inversion of its innermost satellite transition prior to detection with a central transition selective π/2 pulse.…”

Homogeneous broadenings in 2D solid-state NMR of half-integer quadrupolar nuclei

“…This pulse has been used in three different versions of STMAS: the DQF-STMAS and the double-quantum (DQ) STMAS experiments, which only differ by the fact the selective p pulse is at the end (DQF-STMAS) or at the beginning (DQ-STMAS) of the t 1 period [6], and the t 1 -split STMAS for spin 3/2 nuclei [7]. In 1D experiments, the same filtration principle can also be used, simultaneously with a rotor-synchronized acquisition, to enhance by a factor 24/7 the resolution that can be observed for spin S = 5/2 nuclei, leading to the DQF-SATRAS experiment [8]. The comparison of all MQMAS (3QMAS, 5QMAS [9], etc.)…”

“…In all 1D experiments, the homogeneous broadening is equal to 10 6 /pTm 0 , where T is the homogeneous relaxation decay of the observed coherence: CT in MAS and DOR [2], or inner-STs in DQF-SATRAS [8]. This means that for spins 5/2, 7/2, and 9/2, the homogeneous broadening observed in 3QMAS and all STMAS-based 2D experiments will always be larger than with MAS, DOR, and DQF-SATRAS (if T STi % T CT ) 1D experiments.…”