Shift correlation, heteronuclear heteronucleus-detected

Inverse experiments Heteronuclear shift-correlation experiments in which magnetization of the less sensitive heteronucleus (e.g., C) is detected through the more sensitive magnetization (e.g., H). 

Heteronucleus-detected shift correlation experiments have now been largely supplanted by far more sensitive proton- or inverse -detected methods. The heteronu-cleus-detected experiments are now largely reserved, in laboratories with modem NMR spectrometers, for those occasions when very high digital resolution is needed in the carbon frequency domain because of high spectral congestion [109, 110]. The remainder of this section will focus on the now widely utihzed proton-detected heteronuclear shift correlation methods. 

LI Semiselective Refocused Heteronuclear Shift Correlation Spec-troscopy. Semiselective refocusing has recently been employed in heteronuclear spectroscopy for detection of proton-decoupled proton spectra. This allows detection of heteronuclear couplings without complications from proton-proton couplings, and affords spectra with increased sensitivity and resolution. The pulse sequence used is 90°( H)-t-180°( H)-180°(X)-t-90°( H) where X is the heteronucleus. This allows selective refocusing of only those protons which are directly coupled to the heteronucleus. 

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