Free induction decay solvent

Figure 1.13 Increase in receiver gain without solvent signal suppression (a) free induction decay (b) resulting NMR spectrum...

The principle of presaturation relies on the phenomenon that nuclei which are unable to relax, because their population in the ground state a and the excited state (3 is the same, do not contribute to the free induction decay after pulse irradiation. Prior to data acquisition, a highly selective low-power pulse irradiates the desired solvent signals for 0.5 to 2 s, thus leading to saturation of the solvent signal frequency. During data acquisition, no irradiation should occur. NOESY-type presaturation is an effective pulse sequence of presaturation. The pulse sequence consits of three 90° pulses (similar to the first increment of a NOESY experiment) ... 

Figure 1-16 Thefree-induction decay for the H spectra of (a) acetone and (b) methyl acetate, (c) The free-induction decay for the spectrum of 3-hydroxybutyric acid. All samples are without solvent.

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