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Temperature dependency of the Larmor Frequency for protons in NMR

  1. Apr 5, 2005 #1
    Anybody who know something about the temperature dependency of the proton Larmor frequency say for protons in pure water? I am sure people with experience in NMR spectroscopy know. Any good articles/references?

    I am not asking about:

    -temperature dep of the proton density beeing proportional to exp(-hbar omega/k_B T). I.e. the population difference between spin up/down.

    -temperature dep of relaxation effects (T_1 and T_2). E.g. line broadening effects.

  2. jcsd
  3. Apr 5, 2005 #2


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    I thought the Larmor frequency was completely independent of temperature.
  4. Apr 5, 2005 #3
    Outside of the two temperature dependent effects you mentioned i've not heard of anything else.
    Does this mean we are going to have to redesign the MRI machines depending on whether we use them on living people or cold stiffs?? :rofl:
  5. Apr 7, 2005 #4
    Hi Creator!

    I'm not very experienced in the field of MR spectroscpoy but I think I've heard that there are temperature dependent shifts between different peaks in an NMR spectrum. And that one has to take this effect into account when radiating only the water peak. (For example if one has to remove the water peak to see the more interesting weak (about 10 000 times more weak) peaks.)

    The shifts in resonance frequency I'm talking about are small in the sense that typical RF bandwidths used for making MR images are much greater. For "small" temperature differences even on the spatial scale of a pixel. Presumably.
  6. Apr 7, 2005 #5


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    I can imagine temperature dependancy only in the lower order peaks which arise from weaker couplings of different kinds - dipolar, quadrupolar, etc. The proton Larmor frequency itself should only be field dependent.
  7. Apr 8, 2005 #6
    Thanks for the better explanation. I'm not exactly a specialist in NMR either. However, I can see how what you say is possible.
    A nucleus is sensitive to various couplings and motions in the molecular environment in which it rests, and there are several types of 'shifts' in the resonance spectrum due to such variations. So I suppose I can see how it may be possible with high enough resolution to pick up differences in molecular motions..
  8. Apr 14, 2005 #7
    you are looking for the temperature dependence of the line shift. That is the correct term to search through engines.
  9. Apr 14, 2005 #8


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    Oooookay.. I'll stick my dirty nose into this one....

    I think what you want to look for is the Knight shift. However, such effects are usually clearly observed in NMR specturm for metallic substance. So I don't know if this is relevant to the protons in water.

  10. Apr 14, 2005 #9
    another smart word is hiperfine interaction.
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