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Larmor Frequency of 57Fe the earth's ambient magnetic field

  1. Jun 3, 2008 #1
    I would like to determine the Larmor frequency of 57Fe in the earth's ambient magnetic field.

    Properties \ Nuclide 57Fe
    Nuclear Spin, I 1/2
    Nuclear magnetic moment, µ +0.09044
    Gyromagnetic Ratio (rad T-1 s-1) 0.8661 x 10 7
    Quadrupole moment (m2) 0
    Relative Sensitivity (1) 3.37 x 10 -5
    Natural Abundance, % 2.1
    Half-life,T1/2 stable
    Absolute Sensitivity (2) 4.2 x 10 -3
    Frequency (MHz) @ 2.3488 T 3.231

    There is of course an North/South, East/West, and Vertical component which makeup the total magnetic field strength.

    1. How would I calculate the Larmor frequency?

    2. Do all the magnetic field components need to be accounted for?

    I have found related pages on hyperphysics.com but do not have the background to follow everthing presented, therefore, unable to determine the values to plug into the formulas.

    Any help would be greatly appreciated.
  2. jcsd
  3. Jun 5, 2008 #2
    Ok - I'll answer my own question.


    Checking this formula against the above published frequency of 3.231MHz in a 2.3488T field:

    (0.8661E7 / 2pi) * 2.3488 = 3.2377 MHz

    The results are not in exact agreement - off by 6.68 KHz

    Magnetic Field Values
    Horizontal Intensity: 21,033.4nT
    North Component: 20,753.7nT
    East Component: 3418.7nT
    Vertical Component: 48,890.4nT
    Total Field: 53,222.9 nT

    Calculating frequency based on the total field component:
    (0.8661E7 / 2pi) * 53,222.9 = 73.365 Hz

    Calculating frequency based on the vertical field component:
    (0.8661E7 / 2pi) * 48,890.4nT = 67.393 Hz

    From a practical standpoint, there is not that much variation in using the
    vertical Vs total field component.
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