Bulk-magnetization vector

Figure 1.13 (a) Bulk magnetization vector, M°, at thermal equilibrium, (b) Magnetization vector after the application of a radiofrequency pulse. 

Figure 10.2 Representation of excess spin population expressed as a bulk magnetization vector M ...

Figure 10.3 The magnetic field generated by an RF pulse applies a torque to the bulk magnetization vector and drives it towards the transverse plane.

Fig. 1 The basic NMR experiment (A) the rf pulse tips the bulk magnetization vector in the the x-y plane (B) the individual spins start to process according to the frequency determined by their chemical environment (C) the precessing spins are detected along the x-axis as a set of cosine-modulated signals. Fourier transformation of these signals leads to the final spectrum.

Because the small microscopic moments (vectors) from each nucleus add together, what our instrument sees is the net or bulk magnetization vector for the whole sample. We will refer to this bulk magnetization vector in the discussions that follow. 

FIGURE 10.6 The effect of a 90° pulse (M is the bulk magnetization vector for the sample). 

After a 90° pulse, the bulk magnetization vector, M, is directed along the Y axis. The result of this simple experiment should be a single line, since there is only one vector that is rotating at exactly the same frequency as the Larmor precessional frequency. 

As we did in the COSY experiment, we want to allow the magnetization vectors of the protons to process according to different rates, as dictated by their chemical shifts. Therefore, we apply a 90° pulse to the protons, then include an evolution time (ti). This pulse tips the bulk magnetization vector into the Z F plane. During the evolution period, the proton spins process at a rate determined by their chemical shifts and the coupling to other nuclei (both protons and carbons). Protons bound to atoms experience not... 

The fundamental magnetic properties of nuclei are well described elsewhere. I will begin with the bulk magnetization vector M for a series of nuclei of the same type. This is parallel to the external magnetic field Bq and is the resultant of individual magnetic moment vectors fi, precessing about Bq with the Larmor angular velocity... 

Figure 3.4. Effect of applying RF pulse of frequency (Oq for time t seconds on bulk magnetization vector Mq-...

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