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Precession Frequency

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    40886
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    Some nuclei (eg: 1H, 13C) could exist in more than one spin state, which, in the absence of an external magnetic field, have identical energies. For example, 1H nucleus could exist in two spin states, which, in the absence of an external magnetic field, have identical energies.

    precessionfrequency1.png

    In an external magnetic field, they have different energies.

    precessionfrequency2.png

    The frequency corresponding to the difference between the energies of the two spin states, E2-E1, is called the precession frequency.

    precessionfrequency3.png

    Thus, the greater the energy difference between the spin states, the higher the precession frequency. Since the energy difference between the spin states is directly proportional to the external magnetic field (see the graph below), the stronger the external magnetic field, the higher the precession frequency.

    precessionfrequency4.png

    see also resonance


    This page titled Precession Frequency is shared under a All Rights Reserved (used with permission) license and was authored, remixed, and/or curated by Gamini Gunawardena via source content that was edited to the style and standards of the LibreTexts platform.

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