For questions about Nuclear Magnetic Resonance
Questions tagged [nuclear-magnetic-resonance]
125 questions
29
votes
4 answers
How specifically does an MRI machine build an image from received radio waves?
Unlike the excellent Wikipedia page on ultrasound imaging, the one on MRI only explains the principle theory behind MRI - that oscillating strong magnetic fields cause water molecules to emit radiowaves - without explaining how his is applied to…
Mr. Boy
- 1,016
15
votes
2 answers
Decoherence and measurement in NMR
It seems that the Bloch equations, or a suitable generalization thereof, are enough to phenomenologically model the measurement process in NMR. Has anyone attempted a fully quantum mechanical model of the NMR spin system and measurement coil…
Chris Ferrie
- 2,908
11
votes
1 answer
Nuclear Magnetic Resonance (NMR) Conceptual Questions
Let $M$ be the magnetic moment of a system. Below are the Bloch equations, including the relaxation terms.
$$\frac{\partial M_x}{\partial t}=({\bf M} \times \gamma {\bf H_0})_x-\frac{M_x}{T_2} $$
$$ \frac{\partial M_y}{\partial t}=({\bf M} \times…
Rich
- 111
8
votes
1 answer
Why nuclear spin is ignored in Stern-Gerlach experiment?
I can't sure what isotopes of silver(107 or 109) was used.
But Silver has non-zero nuclear spin since the number of proton and neutron are not even.
Since we use Silver atom not electron in SG experiment,
I think we need to consider spin of electron…
min Fe
- 163
6
votes
0 answers
Good books on NMR
I need some help in finding a good book on NMR spectroscopy that focuses more on the physical aspects of the phenomenon and not so much on the chemical application. All the books I've read on that topic include only qualitative explanations, and I'm…
user156550
- 11
5
votes
3 answers
Why thermal tumbling of molecules does not prevent the establishment of magnetization in NMR?
Given the rapid thermal tumbling of water molecules at room temperature, theoretically speaking, why magnetic thermalization of proton nuclear spins is at all possible? Further, how can nuclear spins maintain alignment with the external…
S.G.
- 587
4
votes
2 answers
Why is a nucleus with spin 1/2 spherical?
So i am trying to understand the relaxation mechanism in NMR for nuclei with spin $I>\frac{1}{2}$. I know that nuclei with $I=\frac{1}{2}$ have spherical shape, because many paper have told me so. I guess the argument is that we calculate the…
Luca
- 105
4
votes
1 answer
How to identify an MRI artifact on Fourier space?
I am trying to find the frequency of the artifact on the MRI image of the knee below both manually and with ImageJ:
As you can see the artifact results in a bar pattern extending horizontally along the image - i.e. a spike artifact.
After…
Antoni Parellada
- 954
4
votes
1 answer
How to explain spin-spin relaxation in MRI/NMR in terms of quantum mechanics?
I noticed two approaches to explanation of MRI/NMR. The most popular classical approach exploits the notion of magnetization vector and Larmor precession. Everything then is described as oscillations of this vector relative to static field…
Leonid
- 165
3
votes
1 answer
Could NMR spectroscopy be used to probe a metal?
Obviously most of the nmr radiation would get blocked by the sea of electrons, but
there is still the skin effect where radiation gets in exponentially and could in theory interact with nuclei
the range of the nmr spectrometer is short anyways
and…
user1402154
- 227
3
votes
3 answers
Why the $T_1$ recovery & $T_2$ decay are independent?
In MRI, I was thinking that the decrease in transverse magnetization results in the recovery of longitudinal magnetization.
However, recently, I found it was wrong. I saw a diagram
(McRobbie 2014. Fundamentals of MR Imaging)
and also saw many…
COTHE
- 43
3
votes
2 answers
Theoretical calculation of Electron Paramagnetic Resonance (EPR) spectra
I have read that rather than holding the static magnetic field constant and varying the frequency of the oscillating field in Electron Paramagnetic Resonance/Electron Spin Resonance (EPR/ESR) spectroscopy, the oscillating field is held constant…
slithy_tove
- 384
3
votes
1 answer
Why the angle of nuclear magnetic moment of the proton with an external magnetic field is 54,7°?Why it is not completely parallel to the ext field?
When trying to understand the basics of Nuclear Magnetic Resonance I always found that the angle between the nuclear magnetic moment of the proton and the allied external magnetic field is 54,7° but I cannot find the explanation nor the math to get…
3
votes
1 answer
Does diffusion MRI measure diffusion or osmosis?
I am trying to understand the physical property which is measured in diffusion weighted imaging (DWI) and diffusion tensor imaging (DTI). I read that these methods estimate the apparent diffusion coefficient (in DWI) or the diffusion tensor (in…
srcerer
- 181
3
votes
1 answer
Mathematical term for the on/off gradient functions in MRI imaging
The slice selection gradients, as well as the phase and frequency, in MRI imaging are traditionally represented by on/off box or rectangular symbols:
or
My question is what is the mathematical name for these functions - it would be the equivalent…
Antoni Parellada
- 954