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MAGNETIC NUCLEAR RESONANCE
These two precession positions (parallel and anti-parallel) correspond to the two energy level allowed for a proton in presence of a magnetic field B0, The gap E between theses two levels is a factor of the field intensity. At the thermodynamic equilibrium the lower energy level is the more populated. So, the parallel magnetic moments, which correspond to this level are the more numerous.
A macroscopic moment M – named polarization - results from this population difference. M is parallel to the field direction B0 due to the random repartition of the spins phases. |
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