Signal intensities dephasing

Figure 4. Effect of varying dipolar dephasing time on signal intensity from sea loch sedimentary humic acid.

Figure 5. Effect of dipolar dephaslng on signal Intensities from various carbons in (a), (b) peat and (c), (d) decayed pine leaves. The methoxy (55 ppm) and methyl (20 ppm) signals in conventional spectrum (a) are retained after 40 ps dipolar dephasing (spectrum b). Also acetal resonance (102 ppm) (spectrum a) is lost after dipolar dephasing in (spectrum b). In decayed pine leaf spectra, ketal resonance (105 ppm) in conventional spectrum (c) is retained after 40 ps dipolar dephasing, spectrum (d). (Reproduced with permission from reference 6. Copyright 1983 Pergamon Press.)...

Figure 3.2.20 Scheme of REDOR pulse sequence. Dephasing curve 13C magnetization in 13C- and 15N-labeled glycine as a function of the length of the dephasing time T. A S/S0 (the REDOR difference) is the normalized difference between the 13C signal intensities with and without the 15N pulses. Reproduced with permission from Ref. [51]. 

If the z coordinates of the individual spins at the time of the second field gradient pulse differ from those during the first, then the dephasing of the first field gradient is not completely compensated. This leads to a decrease in the signal intensity, which is indicated in Fig. 7c and d by the broken lines. It is this signal attenuation that is analyzed in the NMR diffusion measurements. 

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