Questions tagged [nuclear-magnetic-resonance]
For questions about Nuclear Magnetic Resonance
74
questions
2
votes
0answers
15 views
Is the Larmor precession of $s$-orbital electrons constant, heedless of additional electronic orbitals as they get added from one element to another?
Understanding how the frequency required in NMR changes from element to element, even if all of them depend on the Larmor precession of the proton, I was wondering if they same applied to electron ...
3
votes
3answers
48 views
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 ...
0
votes
0answers
9 views
Is there an equivalent Larmor precession that is non-magnetic in nature?
Can the magnetic moment of a particle be manipulated without magnetic fields? Could one accomplish this with electromagnetic radiation or even "Atom Lasers"?
0
votes
0answers
12 views
Is the amplitude of the RF pulse affects the NMR signal?
What i knew is that the NMR signal depends on the static magnetic field strength $ B_0 $ (by Boltzmann equation) and its gyromagnetic factor. While the NMR occurs when the RF pulse frequency match the ...
0
votes
1answer
16 views
Integration of Bloch equation in magnetic resonance
From Bloch equation we have
\begin{equation}\label{bloch_01}
\tag{1}
\frac{d M_z}{dt} = \frac{M_0-M_z}{T_1}
\end{equation}
from there we can integrate and we get
\begin{equation}\label{bloch_02}
\tag{...
0
votes
0answers
20 views
Magnetic field measured by NMR
I'm trying to understand some old NMR papers on CrCl$_{3}$ and CrBr$_{3}$ (see [1] and [2]). They did continuous-wave, zero-field Cr$^{53}$ NMR spectroscopy on these compounds, which order either ...
1
vote
0answers
18 views
is room temperature quantum (qubit) nuclear magnetic resonance possible?
I know it is possible to do room temperature NMR. Not just that but one can also use the earth's magnetic field for the nuclei to precess about. If done this way, one gets precession at about the KHz ...
0
votes
0answers
12 views
What affects spin-lattice and spin-spin relaxation times?
I'm performing NMR on common substances like mineral oil, water, and a copper sulfate solution. I know that the ions cause low spin-lattice and spin-spin relaxation times in copper sulfate solution. ...
0
votes
0answers
19 views
Data augmentation in $k$-Space
I am working on denoising data in $k$-space for MRI (magnetic reasonance imaging) using Convolutional neural networks, and I am wondering what would be some suitable data augmentation techniques ...
0
votes
0answers
20 views
Ramsey technique and spin echos
Assuming we use a laser of frequency very close to resonance, in the Ramsey technique (say for 2 level atoms) the $\pi/2$ pulse would put the Bloch vector in the equatorial plane, along the y axis, ...
0
votes
1answer
37 views
What does it mean that the Cauchy probability distribution is connected to the solution of the differential equations of forced resonance?
I have read this (or something like this) in Wikipedia, and found some modelling of inhomogeneities in magnetic fields in clinical magnetic resonance imaging (MRI) through the Cauchy distribution, ...
1
vote
1answer
32 views
Short pulses in NMR - what is their shape?
In the Wikipedia article Nuclear magnetic resonance, section Fourier-transform spectroscopy, it says the following:
Fourier-transform spectroscopy
Most applications of NMR involve full NMR spectra, ...
1
vote
1answer
58 views
Effects of a rotation on a Hamiltonian of a 1/2-spin particle in a magnetic field [closed]
The problem: find how the Hamiltonian $$ H= -\frac{\hbar\omega_0}{2}Z-\frac{\hbar \omega_1}{2}(\sigma_+e^{i\omega t}+\sigma_- e^{-i\omega t}) $$ where $\sigma_{\pm}=\frac{1}{ 2}(X\pm i Y)$ changes ...
1
vote
0answers
13 views
$j$-$j$ coupling interaction in Magnetic Resonance Spectroscopy
I am studying Magnetic Resonance Spectroscopy and I have some difficulties in understanding the j-j coupling interaction. What does actually happen from the physical point of view to the electronic ...
1
vote
1answer
63 views
Phonons and radiation [closed]
I have heard (or misheard) from a reputable Theoretical Physicist from Bell Labs who specialized in Quantum Mechanics that random photon activity can cause decoherence of an entangled or under ...
1
vote
2answers
76 views
Do protons and electrons actually precess?
I know that protons and electrons do not actually spin, although they have the property of spin.
I was learning about MRI. I was introduced to the idea that you have the spin of the proton in the ...
0
votes
1answer
31 views
Tip angle in NMR
Tipping the magnetisation $\vec{M}$ with a $\vec{B}_1$ field for the time $\tau$, results in a tip angle of $\alpha = \omega \tau$ where $\omega$ is the frequency of the $\vec{B}_1$ field. I think I ...
1
vote
1answer
88 views
Angular momentum and magnetic moment [duplicate]
I have just started studying MRI physics and was reading F.Bloch’s paper on Nuclear Induction.
https://doi.org/10.1103/PhysRev.70.460
In page 463, it is mentioned,
To obtain this variation does not ...
0
votes
0answers
11 views
Was NMR/ESR spin flip-flop line ever measured?
Let $a$,$b$ be two unlike spins in a uniform magnetic field and RF excitation, and let $B_0$ be the magnetic field for which some transition energies of the spins coincide $E_a^{i,j}(B_0)=E_b^{k,l}(...
0
votes
0answers
10 views
Q-Populations difference using Boltzmann distribution
Question-
Calculate the difference in the populations of the two nuclear spin states of $1H$ nuclei in a magnetic field of $10T$ at a temperature of $298K$
Answers to chose from (it’s a multiple ...
4
votes
1answer
122 views
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 ...
1
vote
1answer
39 views
Why do 180 degree NMR pulses not violate Einsteins laws for absorption and emission?
So, in Laser theory I learned that a two-level laser is not possible, because it would violate Einsteins equations and the Boltzmann distribution, which in a nutshell say that I cannot cause ...
1
vote
0answers
20 views
Spin-flip of electrons in non-neutral hydrogen atoms in water and fat molecules
What is the Spin-flip of electrons in non-neutral hydrogen atoms in water and fat molecules?
I know there is known spin-flip RF of electrons in neutral hydrogen atoms (hydrogen line).
Thanks,
Cheers
0
votes
1answer
100 views
Why would giving a 90 degree Radiofrequency pulse to a ZERO longitudinal magnetisation cause zero transverse magnetisation in MRI?
Let's imagine in my scenario the (a) in the picture above has no net longitudinal magnetization (therefore 0 longitudinal). Why would giving an 90° RF pulse in my scenario not cause the Protons to ...
2
votes
1answer
31 views
Can nuclear spin interactions drive nuclear transitions?
The atomic nucleus is often treated as monolithic from the perspective of atoms and molecules, but NMR demonstrates that nuclear states can be affected through external means.
Especially the ...
1
vote
1answer
20 views
How to calculate Steady state nuclear magnetization in NMR [closed]
https://en.m.wikipedia.org/wiki/Bloch_equations
In the Bloch Equations M0 is supposed to represent the steady nuclear magnetization. What determines this M0 value and how do you calculate it? Is it ...
1
vote
2answers
266 views
Parallel and Anti-parallel Protons in NMR
I'm an Alevel Student trying to understand the concept of NMRI, I understand that when an external magnetic field is applied, the protons either line up with (parallel) or line up against (...
1
vote
1answer
40 views
On the origin of spin-lattice relaxation
According to P.J. Hore in the Oxford Chemistry Primer "Nuclear Magnetic Resonance" p57, 'the dipolar coupling, modulated by molecular motions, causes nuclear spins to experience time-dependent local ...
1
vote
1answer
161 views
NMR spectroscopy
I was wondering how many times larger is the magnetic moment of an electron compared to a proton? How come the electrons magnetic moment play no role in NMR and MRI? Edit Electron Spin Spectroscopy ...
0
votes
1answer
34 views
Why is the image complex in magnetic resonance imaging? (and how does partial Fourier imaging work?)
The MRI image is reconstructed using inverse Fourier transform from k-space data measured during a pulse sequence. According to some online sources the resulting image is complex-valued and usually (...
0
votes
1answer
12 views
What is responsible for large ppm shifts in HNMR analysis of paramagnetic compounds?
In H-NMR spectra of paramagnetic metal acetylacetonate compounds M(III)(acac)3, large ppm shifts are observed. This is seen with other organometallic compounds as well. What is the origin of this ...
0
votes
0answers
42 views
Quantum Mechanical Treatment of the Spin Echo
I'm trying to find the expectation value of the spin in the $y$ direction after applying a $\pi/2$-$\pi/2$ sequence of pulses. In Slichter's Principles of Magnetic Resonance, he does a $\pi/2$-$\pi$ ...
1
vote
1answer
58 views
Nuclear relaxation time in absence of a magnetic field
It seems that after reading about how MRI scans work, and it appears that I had a misconception of what T1 relaxation times mean. From what I think I understand now, the T1 relaxation time refers to ...
1
vote
0answers
47 views
MRI T1 contrast and k-space understanding
I have a couple of questions regarding MRI theory; I have read around but am struggling to find and answer and move on in my understanding; as such any help would be much appreciated:
When designing ...
2
votes
1answer
543 views
Why do some protons align against the magnetic field?
I was learning about proton NMR (Nuclear Magnetic Resonance Spectroscopy) which is where protons (with their own spins) are subjected to an external magnetic field and a radio frequency is applied to ...
3
votes
1answer
55 views
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 ...
0
votes
1answer
43 views
What is the true way to determine time parameters from semilog graph?
I have experimental nuclear magnetic resonance data that describe T2-relaxation of the nuclei in the sample of interest. The experimental points obey bi-exponential dependence: I = I1*exp(-t/T2_1) + ...
0
votes
0answers
31 views
NMR: Link between relaxation time and Chemical shift
I have been taught NMR in both my physics and chemistry high school classes. Everything lines up until they get into how we detect different chemical environments in the compound.
Chemistry class: ...
1
vote
1answer
41 views
Origin of 2π normalization factor in chemical $J$-coupling compared to the Heisenberg model
In chemistry, particularly the field of NMR spectroscopy, the interaction between two (nucleic) spins (or so I guess?) is governed by the Hamiltonian:
\begin{align}
\mathcal{H}=2\pi\cdot J_{ij}{\vec {...
1
vote
1answer
345 views
Spin precession for Rabi oscillations : interpretation with magnetic field in rotating frame
The model considered
Consider an atom modeled by a two level system of energy $\hbar \omega$. We assume this atom is interacting with an electric field through electric-dipole interaction.
The full ...
0
votes
1answer
33 views
How does an magnetic resonance guided focused ultrasound (MRgFUS) machine work?
As a medical application, magnetic resonance guided focused ultrasound (MRgFUS), is new I the treatment of some parkinsonian diseases, prostate cancer, none problems, and more. However, I am not sure ...
1
vote
0answers
22 views
Continuous NMR Coil arrangement and signal generation
So I am trying to understand how a signal is being produced in CW NMR and I cam across this online
An it talks about how the in CW the spectrum depends only the current being induced in the x-y plane....
0
votes
2answers
174 views
Why do the matrices in k-space and the final MRI image have to match?
Naturally, there is no correspondence pixel-to-pixel between Fourier space (k-space) and the final 2D image of an MRI - k-space stores the Fourier coefficients, hence each pixel in it affects the ...
0
votes
1answer
19 views
Dose attenuation decrease frequency
What cause the transveres decay in nmr? From wiki I have an understanding that it has somthing to do with decoherence which is caused by spin of one atom effecting anouther.
That my basic understand,...
0
votes
1answer
396 views
How does a gradient elicit a RF signal from the stimulated tissue in MRI?
I understand the idea of spatial encoding afforded by the application of a readout gradient along one of the planes (frequency direction) in MRI. In typical 2D image generation, there is also a phase ...
0
votes
1answer
39 views
How can I calculate the total rotation a detuned pulse will apply a nuclear spin?
I'm trying to model the effect a radiofrequency pulse will have on a nuclear spin at different detunings. The pulse has a sech lineshape, a pulse area (time integral of the pulse envelope) of $\frac{π}...
2
votes
1answer
346 views
How can a frequency-specific interference in MRI be limited to a single stripe on the corresponding image (zipper artifact)?
The so-called herringbone or spike MRI artifact on a given example could be traced to a specific point(s) in Fourier space ("k-space").
The idea is that during the acquisition of the image, a certain ...
4
votes
1answer
356 views
How to identify an MRI artifact on Fourier space? [closed]
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 ...
3
votes
1answer
83 views
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 ...
2
votes
1answer
161 views
From K-space to wavelets in compressed SENSE MRI (cSENSE)
In compressed sensing MRI (cSENSE MRI) technology the idea seems to entail sampling from the Fourier domain (k space) in a way that, when transformed to the wavelet domain ("sparsification"), the ...
