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Fourier-transform mass spectrometry takes advantage of ion-cyclotron resonance to select and detect ions.
Ions in a magnetic field will move in a circular path of radius:
r = mv/eB
f = eB/m
Ions moving at their cyclotron frequency can absorb RF energy at this same frequency. A pulse of RF excites the ions in the magnetic field. The ions re-emit the radiation, which is picked up by the reciever plates. The decay produces a free-indcution decay signal that can be Fourier transformed to produce the emitted frequencies, and therefore the masses of the ions present.
Schematic of a FT-MS
FTMS can provide very high resolution, 106, which its main advantage compared to other mass spectrometers.
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