Static linewidth signal

The superposition of the different magnetic interactions complicates the interpretation and calculation of the resulting normalized line shape function,/(v). It is therefore advantageous to make use of the so-called second moment M2 as a measure of the linewidth of the solid-state NMR signals. The full-width at halfmaximum of an NMR signal in frequency units, also called the static linewidth, is... 

Figure 34 shows spectra of TA and SOL from a 24-year-old male volunteer recorded at 1.5 T (a) and 3.0 T (b). Besides the clearly improved SNR, which is elevated by a factor of 1.7 to 1.8 at 3.0 T, distinct differences can be observed for the two magnetic field strengths In both muscles, IMCL and EMCL are clearly better separated at 3.0 T as the methylene resonance of IMCL shows smaller natural linewidths (in ppm). However, EMCL signals remain with a broad lineshape in TA as well as in SOL, since the lineshape is dominated by susceptibility induced static field inhomogeneities. Crs and TMA signals are... 

In addition to the induced magnetic field, the migration rate can greatly influence the NMR signal intensity and linewidth. Unlike in LC, the rate of migration of each band in CE is characteristic of electrophoretic mobility and so each move past the detector at different rates. The effective longitudinal (7ie(f) and transverse relaxation (T a) times of NMR nuclei in a flow system can be related to the residence time of the analyte (x) in the detector and the relaxation times (7 b 7 2) under static conditions [45] ... 

The simulated spectra in Fig. 9.8 illustrate the effect of MAS for the case of a CSA interaction. Upon rotating the sample, the static lineshape is seen to break up into a centreband and spinning sidebands, separated by the rotor frequency. At a low MAS frequency, yj, the sideband manifold is observed to map out the shape of the static pattern. As the Vr is increased, the signal intensity is increasingly concentrated at the centreband position, which corresponds to the isotropic chemical shift. It is to be noted that the linewidths are narrow and independent oftR [22]. 

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