Proton dipolar decoupling

However, it is found that a combination of techniques, such as proton dipolar decoupling (removes the dipolar interactions), magic angle spinning (reduces the chemical shift tensor to the isotropic chemical shift value), and cross-polarization (increases the sensitivity of rare spins, like 13C) applied to a solid state material, results in sharp lines for 13C nuclei in the solid state10). Thus, the observation of narrow lines or high resolution NMR in the solid state is possible. 

Figure 14.11 Basic 2D pulse sequence used for the measurement of residual dipolar local fields. After the excitation pulse the spins are allowed to evolve for some time tj (indirect dimension) under influence of the relevant spin interactions before crosspolarisation takes place. The direct detection during time t2 then takes place on the 13C side typically under proton dipolar decoupling (DD). The basic scheme can be extended by various spin manipulation techniques (not shown) during time tj. For instance, the heteronuclear dipolar contribution can be removed by a decoupling pulse...

Silicon NMR measurements were made at 39.5 MHz on a Jeol FX200WB spectrometer using the combined techniques of magic-angle sample spinning and proton dipolar decoupling. All samples were examined in the fully hydrated state. Chemical shifts were referenced to sodium 4,4-dimethyl-4 silapentane sulfonate taken to... 

Si NMR spectrum at 39.5 MHz with magic angle spinning and proton dipolar decoupling of ZR4 with Si/Al (elemental) = 1.66. 

Figure 5. Proton dipolar decoupled and cross polarized NMR spectra (24.3 MHz) at 25°C of poly(dAdT) poly(dAdT) fibers (right) and sal n sperm DNA fibers (left). The top spectra are from the fibers oriented perpendicular to the magnetic field in a teflon holder, and the bottom spectra are from parallel orientation. Humidity was controlled. (Reproduce, with permission, from Ref. 17.

High-resolution solid-state NMR is also a very interesting tool for studying non-oriented polymer liquid crystals. Proton dipolar decoupling (DD), which suppresses the dipolar broadening, and rapid... 

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