Heteronuclear decoupled version

Prior to the advent of 2D methods, selective spin decoupling was used extensively in both proton NMR and in heteronuclear (especially 13C) NMR to ascertain which sets of nuclei contribute to observed spin coupling. Such information is critical to assignment of resonances and to the elucidation of the structure of an unknown molecule. 2D methods now largely supply this information much more efficiently, by correlations that depend on the existence of spin coupling. The homonuclear version of one such experiment is called COSY (correlation spectroscopy), and the heteronuclear version is known by several acronyms, most commonly HETCOR (lieferonuclear correlation). 

There is also a heteronuclear version of the 7-resolved experiment, known as HET2DJ. The most common examples involve the spectrum displayed as decoupled singlets... 

The use of high-power resonant RF to collapse coupling interactions to zero. Versions include homonuclear (observed and decoupled nuclei have the same y), heteronuclear (observed and decoupled nuclei with different y), and noise (for wide frequency coverage). With low-power selective irradiation it is possible to map coupled-energy diagrams and transfer polarization. 

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