Temperature dependency of the Larmor Frequency for protons in NMR

In summary: That could be a better search term.In summary, the proton Larmor frequency is dependent on temperature. One has to take this effect into account when radiating only the water peak.
  • #1
stupido
2
0
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.

Stupido.
 
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  • #2
I thought the Larmor frequency was completely independent of temperature.
 
  • #3
stupido said:
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.

Stupido.

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?? :smile:
 
  • #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.
 
  • #5
stupido said:
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.

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.
 
  • #6
stupido said:
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...

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..
Creator
 
  • #7
Creator said:
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..
Creator
you are looking for the temperature dependence of the line shift. That is the correct term to search through engines.
 
  • #8
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.

Zz.
 
  • #9
another smart word is hiperfine interaction.
 

Related to Temperature dependency of the Larmor Frequency for protons in NMR

1. Why is the Larmor Frequency temperature dependent?

The Larmor Frequency, which is the frequency at which protons precess in a magnetic field, is temperature dependent because temperature affects the magnetic properties of the surrounding environment. As temperature increases, the magnetic field strength decreases, resulting in a lower Larmor Frequency.

2. How does temperature affect the Larmor Frequency?

As temperature increases, the Larmor Frequency decreases. This is because at higher temperatures, the thermal energy causes the magnetic moments of the surrounding atoms to become more randomized, resulting in a weaker magnetic field and a lower Larmor Frequency.

3. What is the relationship between temperature and the Larmor Frequency?

The relationship between temperature and the Larmor Frequency can be described by the equation: ω = γB0, where ω is the Larmor Frequency, γ is the gyromagnetic ratio of the proton, and B0 is the strength of the external magnetic field. As temperature increases, B0 decreases, resulting in a lower Larmor Frequency.

4. Why is it important to consider the temperature dependency of the Larmor Frequency in NMR experiments?

It is important to consider the temperature dependency of the Larmor Frequency in NMR experiments because accurate measurements of the Larmor Frequency are essential for obtaining reliable and precise results. If the temperature is not taken into account, the Larmor Frequency may be incorrectly calculated, leading to inaccurate data and conclusions.

5. How can the temperature dependency of the Larmor Frequency be compensated for in NMR experiments?

In order to compensate for the temperature dependency of the Larmor Frequency in NMR experiments, the temperature can be controlled and kept constant during the experiment. Additionally, the temperature coefficient of the magnetic field can be determined and used to correct for any changes in the Larmor Frequency due to temperature variations.

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