Abstract
All nuclei whose mass number is not divisible by 4 have a nuclear magnetic spin (NMS) moment. The magnitude of this moment depends on the kind of nucleus. If a chemical system containing equal nuclei with an NMS is brought into a strong magnetic field, then the direction of these moments is (at least partially) aligned. When a tunable microwave source is arranged perpendicular to the magnetic field, the spins of the aligned nuclei will flip over at a defined micro-wavelength. (This is not a periodic process. With intense microwave radiation we observe spin saturation.) The exact value of this wavelength is influenced by the chemical neighbourhood of the nucleus in question (chemical shift) as well as by adjacent nuclear spins (spin-spin coupling). The position of a resonance is given on the abscissa relative to a standard, usually tetramethylsilane (= 0). The (maximal or integrated) intensity of a resonance peak is proportional to the amount of nuclear spins being in resonance. This is important for quantitative analyses.
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