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1.6: How does precession generate the macroscopic magnetization (Mo)?

  • Page ID
    77751
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    If we now examine what we would expect for an ensemble of nuclei, the magnetic moments of the +½ spins will be aligned with the applied magnetic field, while the moments of the higher energy –½ spin state will be opposed to Bo. However, all the spins in our sample will be precessing randomly about Bo at their Larmor frequency as illustrated in the figure below. Because slightly more of our nuclei are in the lower energy +½ spin state, if we take the vector sum of all the magnetic moments we will realize a single vector pointing in the direction of the applied magnetic field called the macroscopic magnetization, Mo. The macroscopic magnetization then provides a way to visualize the population difference of our spins. It is this macroscopic magnetization vector that is manipulated in the NMR experiment.

    macroscopic magnetization.PNG


    This page titled 1.6: How does precession generate the macroscopic magnetization (Mo)? is shared under a CC BY-NC-SA 2.5 license and was authored, remixed, and/or curated by Cynthia K. Larive & Albert K. Korir via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.