Pulse sequence gated decoupler method

Figure 9. Pulse sequence used in acquiring the spectrum of Figure 8 this "gated decoupler" method for heteronuclear 2D J spectroscopy results in the multiplet splittings in fj appearing to be halved.

There are several types of heteronuclear 2D J-resolved experiments (i) the gated decoupler method, (ii) the spin-flip method, (iii) the selective spin-flip method, (iv) the semi-selective spin-flip method, and (v) the use of polarization transfer, e.g., INEPT. In all these experiments, the pulse sequence results in the generation of spin echoes which are modulated during the evolution period by coupling frequencies. 

Figure 5.43. Gated decoupler method for recording 2D J-resolved C-NMR spectra. The upper portion shows the pulse sequence while the lower portion represents the effect of the pulse sequence on magnetization of a CH group decoupling during the preparation period provides nuclear Overhauser enhancement. The position of the two magnetization vectors in (d) will be dependent on 11 the sum of the two vectors which is detected will depend both on and the magnitude of the coupling constant, J. The signals are then said to be J-modulated. ...

H and 19F NMR spectra are recorded with a normal one-pulse sequence or, alternatively, the XH spectra are recorded with a sequence that allows simultaneous solvent suppression with presaturation (31) or a sequence that includes some other method of suppression 13C 1H and 1P 1H spectra are recorded with proton broadband (composite pulse) decoupling (32), and 31P spectra with gated proton decoupling (33). 

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