Continuous-Wave CW NMR Spectrometry

FIGURE 4.1. Spinning charge on proton generates magnetic dipole. 

FIGURE 4.2. Two proton energy levels, from quantum mechanics, in a magnetic field of magnitude B0. N is population. The direction of the magnetic field ( ] f ] ) is up, parallel to the ordinate, and B ) increases to the right. 

The radiofrequency vx can be introduced either by continuous-wave (CW) scanning or by a radiofrequency pulse. 

An assemblage of equivalent protons precessing in random phase around the z axis (i.e., in the direction of the stationary magnetic field B )) has a net macroscopic magnetization M0 along the z axis, but none in the xy plane (Fig. 4.4). 

When an applied rf (r,) is equal to the precessional frequency of the equivalent protons (Larmor frequency vL in MHz), the state of nuclear magnetic resonance is 

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