NMR: what is the area under the curve of the radio transmitter?

  • Thread starter bhimberg
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Main Question or Discussion Point

Using two pernament magnets, a transmitter coil and a pickup coil, we applied a match filter to find the resonant frequency (our sample was wrapped in the pickup coil with the trasmitter stationary wrt it: the magnets are the round type, ceramic I think). Using this frequency we can map the strength of the magnetic field.

Two sets of data were taken, one was the frequency at each point, another was the area under the curve on channel 1 of the osilliscope. Channel one is the output of the pickup coil: the coil around the sample that absorbs the photons created by the nuclei when they return to their ground state.

What I don't understand is what the area under this curve represents. The magnetic field appears to be nearly uniform (with small variances that result in the resonant frequency changing from 15.52 Mhz to 15.55 Mhz), yet this area has a peak near the center of the magnets, a magnitude of around 1600, and drops off radially to the edge, a magnitude of 60.

Units on the scope are volts*seconds, though I *think* the prof may have mentioned they were volts*seconds*meters (which doesn't make sense). It may have something to do with magnetic flux, but if there were the case then it too would be unifor since the field is uniform, correct?
 

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