Nuclear magnetic resonance <unk>  in the geomagnetic<unk>  is conventionally referred to as<unk>  (EFNMR). Note that the same acronym is used for electric<unk> <unk> .
EFNMR is a special case of low<unk> <unk> .
When placed in a constant magnetic<unk>  and stimulated (perturbed) by a pulsed or alternating magnetic<unk> ,<unk>  active nuclei (such as 1H or 13C) resonate at frequencies characteristic of the isotope. The resonant frequencies and signal strengths are proportional to the strength of the applied magnetic<unk> . Thus in the 21 tesla magnetic<unk>  that may be found in high resolution laboratory<unk>  spectrometers, protons resonate at 900 MHz. However in the<unk> 's magnetic<unk>  the same nuclei resonate at audio frequencies of around 2 kHz, generating very weak signals.
The location of a nucleus within a complex molecule affects the chemical environment experienced by the nucleus. Thus different hydrocarbon molecules containing<unk>  active nuclei in different positions within the molecule produce slightly different patterns of resonant frequencies. Analysis of the frequency spectrum allows the structure of the molecule to be determined.
Earth's field NMR
Nuclear magnetic resonance spectroscopy
Nuchal scan
MUGA scan
Carbon-13 NMR
MRI sequences
Electromagnetic spectrum
In vivo magnetic resonance spectroscopy