TOtal Suppression of Sidebands

Fig. 8 Schematic diagrams for the following pulse sequences (A) single pulse excitation/magic-angle spinning, (B) total suppression of sidebands, and (C) delayed decoupling, or dipolar dephasing.

Abbreviations BCC. body centered cubic DOS. density of states ESR. electron spin resonance HX.AI S, extended X-ray absorption fine structure F CC. face centered cubic (a crystal structure). FID, free induction decay FT, Fourier transform FWHM, full width at half maximum HCP, hexagonal close packed HOMO, highest occupied molecular orbital IR, Infrared or infrared spectroscopy LDOS, local density of states LUMO, lowest unoccupied molecular orbital MAS. magic angle spinning NMR. nuclear magnetic resonance PVP. poly(vinyl pyrrolidone) RF. Radiofrequency RT, room temperature SEDOR, spin echo double resonance Sf, sedor fraction SMSI, strong metal-support interaction TEM. transmission electron microscopy TOSS, total suppression of sidebands. 

In MAS, the sample is rotated rapidly by mechanical means around an axis that makes a prescribed angle with the static field. If the sialic spectrum (at rotation speed zero) has contributions from second-order tensor interactions such as the chemical shift anisotropy, then MAS breaks these contributions into a series of sidebands, separated from the average resonance frequency by multiples of the rotation frequency (/). The envelope of these sidebands traces out the original second-order tensor. At high rotation speeds, all sidebands are outside the static spectrum and therefore have zero amplitude so that only the average resonance survives. It is not always technically possible to reach such speeds in such cases the intensity of the sidebands can be diminished by applying certain pulse sequences [total suppression of sidebands (TOSS)] (see section IV.D). 

WT Dixon, J Schaefer, MD Sefcik, EO Stejskal, RA McKay. Total suppression of sidebands in CPMAS carbon-13 NMR. J Magn Reson 49 341-345, 1982. 

The CP step is an essential building block for pulse sequences in solid-state NMR. The easiest ID experiments that are routinely used for characterization of organic, organometallic and hybrid solids are total suppression of spinning sidebands (TOSS), nonquatemary suppression, and so on. 

The pulse sequence used most often for this purpose is the TOSS sequence (total suppression of spinning sidebands. Fig. 3.3.9) [Dixl, Gril]. Before the start of data acquisition at r = ts the spin system is prepared by four 180° pulses at well-defined times... 

A number of ingenious pulse techniques have been devised to eliminate sidebands from high-field spectra so that normal CP/MAS spectra are generated. These are referred to as PASS (Phase Alternated Sideband Suppression) and TOSS (TOtal Sideband Suppression) techniques. An example of the use of TOSS to suppress sidebands from the aromatic carbons in Illinois No. 6 coal is shown in Fig. 3. Two different spinning rates were... 

Figure 10.6 Top Palmitic acid nicotinamide heterodimer formed in the 1 1 co-crystal (Cambridge Structural Database (CSD) ref code JEMDIP), bottom CP-HETCOR spectrum of palmitic acid nicotinamide 1 1 co-crystal. ID H MAS (Vf = 35 kEQz) and CP-TOSS (Cross Polarization-TOtal Sideband Suppression) (Vr = 8 kBz) spectra are shown as projections (adapted from Vogt et ai, ref. 43 copyright 2008 American Chemical Society).

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