Wide line separation experiment

In the solid, dynamics occurring within the kHz frequency scale can be examined by line-shape analysis of 2H or 13C (or 15N) NMR spectra by respective quadrupolar and CSA interactions, isotropic peaks16,59-62 or dipolar couplings based on dipolar chemical shift correlation experiments.63-65 In the former, tyrosine or phenylalanine dynamics of Leu-enkephalin are examined at frequencies of 103-104 Hz by 2H NMR of deuterated samples and at 1.3 x 102 Hz by 13C CPMAS, respectively.60-62 In the latter, dipolar interactions between the 1H-1H and 1H-13C (or 3H-15N) pairs are determined by a 2D-MAS SLF technique such as wide-line separation (WISE)63 and dipolar chemical shift separation (DIP-SHIFT)64,65 or Lee-Goldburg CP (LGCP) NMR,66 respectively. In the WISE experiment, the XH wide-line spectrum of the blend polymers consists of a rather featureless superposition of components with different dipolar widths which can be separated in the second frequency dimension and related to structural units according to their 13C chemical shifts.63... 

Wide Line Separation Spectroscopy (WISE). Wide line separation spectroscopy (WISE) has been applied to correlate the molecular structme and mobility based on the linewidths of static H lines (Figme 48). In this experiment H lines are separated by virtue of a much better resolved chemical shift of C sites in their close proximity. The linewidths of H peaks provide a qualitative estimation of mobility (the wider the peak, the stronger the H H coupling and, hence, a reduced mobility), while the well-resolved C sites provide the information on molecular structme. 

The focus of the chapter then shifts to heteronuclear 2D correlation (HETCOR) experiments. The evolution of single quantum coherence (SQC) of two different nuclei in these experiments with a coherence transfer step provides the basic formula for these correlations. In WISE (wide line separation), a wide dipolar... 

The last example of 2D techniques presented here is the wide-line separation (WISE) experiment [26, 49]. In a WISE spectrum, high-resolution C-CPMAS... 

Fig. 15. The pulse sequence for the 13C 2H correlation experiment.38 This two-dimensional experiment, conducted under magic-angle spinning, separates 2H line-shapes according to the 13C isotropic chemical shift of nearby l3C spins, i.e. the bonded l3C in practice. The narrow black pulses are 90° pulses wide ones are 180° pulses. The 2H pulses are placed symmetrically within the rotor period.

Different adhesives were checked and "Bison" has been found the strongest. Nevertheless in testing the tabbed 3D carbon-fiber specimens, the separation of the tabs from the specimen surface before the crack initiation was observed in all initial experiments. To prevent this, side-grooved specimens were used. The 1 mm wide side grooves were machined by milling cutter. The depth of grooves equal to 4 mm was chosen to cut the side lines of transverse yams leaving intact only 2 transverse yarn lines. 

---