Sample Excitation and the Rotating Frame of Reference

Recall from Chapter 1 that, once the net magnetization vector is tipped away from equilibrium along the z-axis and has a component in the xy plane, it will feel a torque from the applied field Bq and 

J usl a small amounl from its equilibrium position along z  

Off resonance. A spin is off resonance when the spin s resonant frequency is not at the center of the spectral window (the center of the spectral window corresponds to the frequency of the rotation of the rotating frame of reference). 

I FIGURE 2.6 Pulse roll-offattenuates signals far from on-resonance. 

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