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Set 6 – Classical Description

  • Page ID
    79281
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    1. What happens when an electrical current is run through a wire coil?
    2. What happens to the nucleus after B1 is turned off?
    3. Suppose a wire coil is placed on the Y-axis.What happens in the wire coil as the magnetic field of the tipped nucleus is imparted on it?
    4. Draw the current profile that would result in the wire coil on the X-axis as the tipped nucleus relaxes back to its ground state.
    5. Draw the FID that would result if the nucleus had a much shorter relaxation time.
    6. Do you see a problem with performing a FT on an FID with a very short relaxation time?If so, what would happen in the resulting frequency domain spectrum?
    7. Where is the amplitude of peaks determined in the FID?
    8. Why is a delay time incorporated into the sequence?
    9. Why are the advantages and disadvantages of using 30o pulses instead of 90o pulses?
    10. What is the advantage of recording several FIDs and adding them together?
    11. Suppose the following pulse sequence is used to obtain the spectrum of a 13C nucleus with a spin-lattice relaxation time of 100 seconds (90o pulse, 1 second collection of the FID, 1 second delay).Note, carbon atoms with no directly bonded hydrogen atoms can have relaxation times as long as 100 seconds.This pulse sequence is repeated four times.
    • Draw the position of the 13C magnetization vector after each of the four pulses.
    • Draw the corresponding FID that would be obtained after each pulse.
    • Draw the composite FID obtained by adding the four individual FIDs together.
    • What do you observe for this carbon in the resulting frequency domain spectrum?

    This page titled Set 6 – Classical Description is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Thomas Wenzel via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.