D 2H Natural Abundance, Sensitivity

Hydrogen has two NMR-active nuclei H, always known as the proton (thus proton NMR ), making up 99.98%, and 2H, normally referred to as D for deuterium. 

These absorb at completely different frequencies, and since deuterium and proton chemical shifts are identical (also because deuterium is a spin-1 nucleus), deuterium NMR spectra are hardly ever measured. 

However, NMR spectrometers use deuterium signals from deuterium-labelled molecules to keep them stable such substances are known as lock substances and are generally used in the form of solvents, the most common being deuterochloroform CDCl3. 

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