1.5: What is Precession?
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A spinning charged particle creates a magnetic field, called the magnetic moment, µ. This magnetic moment is a vector quantity that is proportional to the angular momentum: \(µ = γp\). Because our nucleus has angular momentum, the magnetic moment, depicted as the red vector in the figure below, will appear to precess (or rotate) about the applied magnetic field \(B_o\). This precession is analogous to the motion of a spinning top. The frequency of precession is dependent only on the type of nucleus (defined by the gyromagnetic ratio, \(γ\)) and the value of \(B_{eff}\), as defined in Equation \(4.1\). The precession of a single nucleus, depicted as a blue sphere spinning about its axis, is shown here.