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Larmor frequency in NMR for nucleus with spin greater than 1/2

I'm reading the theory about NMR and in most textbooks I can see that the Larmor frequency achived as follow: on the one hand from QM we know that $$\Delta E = \hbar \omega $$ on the other hand, if ...
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Is precessional frequency of hydrogen nucleus in H-NMR equal to angular frequency of magnetic component EM radiation?

I asked the same question on chemistry stack exchange but got no answer over there. So, I'm posting it here in the hopes that I'll find some sort of answer:) Suppose we have a hydrogen nucleus. Now, ...
Natasha J's user avatar
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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. ...
COTHE's user avatar
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Is the generation of NMR signal due to spontaneous emission?

The usual description of how NMR signal is generated is that the sample has some equilibrium magnetisation along the $z$ axis, this is then flipped into the $x$-$y$ plane by a 90° pulse and there it ...
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Distribution of relaxation time in a stretched exponential function

I'm fitting a stretched exponential function to a saturation recovery experiment, of the following form: $$ I(t)=I_0 \left(1-\exp\left(-\frac{t}{T_1}\right)^\beta\right) $$ Where $ \beta $ ranges from ...
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Longitudinal relaxation in NMR - a quantum description?

I'm currently reading Understanding NMR Spectroscopy by J. Keeler and in the section about longitudinal relaxation, he writes that (using $n_i$ for the population of state $i$) the rate of change of $...
FusRoDah's user avatar
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Forms of interaction between two spins

I am learning the principles of nuclear magnetic resonance, and came across the interaction between two Hydrogen nuclear spins, which affects the relaxation properties of materials like water in NMR. ...
night cat's user avatar
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Why does saturation occur when the populations of the spin-up and spin-down energy levels are equal?

I'm learning about NMR spectroscopy and I don't understand why saturation occurs when the populations of the higher and lower energy levels of spin are equal. Why wouldn't energy continue to be ...
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Line Width of Resonance Peak in NMR Experiment

I'm studying the NMR experiment at the moment and was wondering what the line width of the resonance peaks represents? When I've looked into it, it just comes up with the definition that it's 'the ...
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What is "point of interest" and why isn't there a Zref for determining electron beam quality with TRS 398?

What is "point of interest" and why isn't there a Zref for determining electron beam quality with TRS 398? ((To what depth do you put the ion chamber when you do high energetic electron ...
medical physics's user avatar
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Slice selection in MRI

Studying MRI, I found that excitation is done by applying B1 (RF) and Gz simultaneously. But, I think that if those are applied at same time, slice selection cannot be done correctly because Gz will ...
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Why is 180 degree pulse applied after half echo time (TE) in Spin Echo sequence?

The definition of Echo Time from Radiopaedia: The echo time (TE) refers to the time between the application of the radiofrequency excitation pulse and the peak of the signal induced in the coil. It ...
HelpNeederStudent's user avatar
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How (mathematical relation) and why (mechanism) do Time-to-Repetition (TR) and Time-to-Echo (TE) affect Signal-to-Noise-Ratio (SNR)?

I want to understand why (what is the mechanism behind) lowering the time to echo (can we actually have T1-weighted Zero Time to Echo images) increases the Signal to Noise Ratio in (nuclear) Magnetic ...
George Ntoulos's user avatar
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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) ...
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ESR Half Field Transition

I am studying ESR with Atherton. While reading the book, I found something weird (at least to me). Can anyone help me with this? What I know is that $M_S = 2$ transitions can occur because at low ...
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Does the RF magnetic field have to be uniformly constant for a coherent EPR signal

Consider a loop gap resonator for electron paramagnetic resonance which has static (but sweepable) magnetic field in one direction, "x", and a GHz RF magnetic field in a direction "z&...
Tunneller's user avatar
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Larmor precession with an oscillating field?

With a non-polar molecule like CO2, presumably Larmor precession doesn't apply. However, CO2 has a mode of vibration that induces an oscillating dipole moment. Could something similar to Larmor ...
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Does a moving atom with a nuclear magnetic moment generate an electric field?

I have read that moving ions generate a magnetic field as it moves. Similarly, is this also true regarding the nuclear magnetic moments of the atom? In other words, would a moving atom with a nuclear ...
Young Jun Lee's user avatar
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Why is water diamagnetic, but water protons align with external field in NMR?

I recently re-learned today that water is diamagnetic. I don't believe I totally understand why, but I will accept it as true. However, I remember that in NMR of water, the protons of water form ...
jmd's user avatar
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An embarassing question about photon power, Hamiltonians, and converting units

I am a hapless experimentalist, and desperate for a bit of advice. I am trying to do a spin-density calculation building on some of the ideas contained in this paper. In brief, it's describing a ...
Landak's user avatar
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Working of MRI in detection of tissues for imaging

why we consider the rotational axis of proton under the action of magnetic field in MRI not electron?
Nikku's user avatar
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What is the "envelope" of the magnetic field, in NMR?

Let $B_1$ be RF pulse. According to the following lecture, $B_1^e$ represents the "envelope" of $B_1$ and under the labo-frame coordination, following be satisfied; $B_1\left(t\right)=B_1^e\...
Blue Various's user avatar
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How is a 180° RF pulse in NMR?

A 180° pulse appears to be an RF pulse that is equivalent to rotating the direction of the magnetization vector by exactly 180° in MRI or NMR observations; That is, it may invert the direction of the ...
Blue Various's user avatar
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147 views

What is the required RF power pulse to flip the nuclei from longitudinal to transverse in MRI scanning?

Picture source: Lesics at t=189 and t=205. I recently visited a friend who just had MRI scan. From his explanation, I have some question about magnetic power applied to him. Consider a B magnetic ...
AirCraft Lover's user avatar
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100 views

In MRI, why are outputs of slice selection and frequency encoding different although both use gradient?

I am a cognitive science graduate student who began to study MRI with a little physics background. Please forgive me if I don't use proper verbs or prepositions. I think I understood slice selection ...
Andy Junghyun Kim's user avatar
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1 answer
195 views

How does one pick Echo time (TE) in MRI machine?

The definition of echo time (TE) in MRI is the time difference between a 90-degree RF signal and the echo peak, which feels like an intrinsic property of the proton. How can we even control how long ...
yupbank's user avatar
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1 answer
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Why is water bright in a T2 weighted image?

I am new to study MRI. Please understand if some terminologies I use are wrong. This might be a silly question, but I wonder why water is bright in a T2 weighted image. T2 relaxation is also called ...
Andy Junghyun Kim's user avatar
2 votes
2 answers
730 views

What is 90 or 180 "degree" RF pulse in MRI?

I am studying MRI, specifically spin echoes. Now I kind of understand how magnetic resonance imaging works, but what I'm stuck is the definition of "degree" in MRI. What I thought was that ...
Andy Junghyun Kim's user avatar
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1 answer
71 views

Recovering Decay Constant from Fourier Transformed Exponential Decay in NMR

I'm currently in a NMR lab for an undergraduate physics class, and I am attempting to determine the decay constant $\tau$ (e.g. $T_2$) associated with a free induction decay signal. However, our ...
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How is NMR different from hyperfine structure?

Essentially I've confused myself by trying to understand NMR (nuclear magnetic resonance) as the transition between hyperfine levels and I seem to encounter a contradiction. I'll describe my ...
AXensen's user avatar
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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 ...
Javier Sánchez 's user avatar
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1 answer
168 views

Why does transversal magnetization decay and what is actually being measured in an MRI sequence? [closed]

This may be a few questions disguised as one however this may help uncover what's the missing piece in my understanding. $T1$ characterizes the rate at which longitudinal $M_z$ recovers and $T2$ ...
Ilisuan Iannis Patriciu's user avatar
2 votes
1 answer
63 views

Why isn't amplitude modulation used more often in magnetic resonance technologies? [closed]

Optically pumped magnetometers utilize a visible light carrier wave which is amplitude modulated down to a Larmor frequency of ~1000 Hz. This is in contrast to the vast majority of magnetic resonance ...
Tymir's user avatar
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Magnetic Resonance in quantum mechanics [closed]

Using the identity ($I$) and the Pauli operators ($\sigma_{i}$) as a basis, the Hamiltonian of any two-level system (of basis states $\{|0\rangle,|1\rangle\}$) can be expressed as follows $$ H =\frac{\...
QuantionQuestums's user avatar
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1 answer
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What is the oscillation frequency of the observed/measured free induction decay signal in MRI?

I recognize that many articles attempting to describe the basics of MRI under simplify a lot of technical details. I would like to confirm the following understanding about the free induction decay ...
S.C.'s user avatar
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1 answer
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Mechanism of NMR

I am doing research into NMR right now in several different sources, and it seems as if there are two competing models which are used to describe how radio waves can impact nuclear spins. The first ...
slithy_tove's user avatar
2 votes
1 answer
95 views

Spectral density of random fluctuations

In nuclear magnetic resonance relaxation theory, in order to determine relaxation rates from transition probabilities, one needs the spectral density of random magnetic field fluctuations around the ...
Yuri Shakhman's user avatar
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1 answer
52 views

NMR without static magnetic field

NMR is usually conducted by first aligning nuclei to a strong, constant magnetic field, so that you can apply RF radiation with a magnetic component directly perpendicular to the constant field. ...
slithy_tove's user avatar
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1 answer
351 views

Proton spin precession and alignment to magnetic field in NMR

Precession due to magnetic field occurs when the magnetic moment of a small coil is proportional to its angular momentum ($\vec{m}=g\vec{L}$). This is due to Euler momentum equation, which for such a ...
Salvatore Manfredi D's user avatar
2 votes
2 answers
310 views

How are the Bloch equations non-linear?

This question is similar to the following, but I have expanded the question moderately: Nonlinearities arising from linear equations The Bloch equations are described by the following vector equation (...
jmd's user avatar
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1 answer
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How does MRI distinguish information between in-plane localization and slice selection, despite both using frequency encoding?

A MRI machine can generate 3D image of a human brain. A 3D image have three axis x (horizontal), y (vertical) and z (head-foot). First, a slice along z were selected using frequency encoding. Then, ...
John Smith's user avatar
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1 answer
292 views

What is the function of the RF pulse in NMR?

I am slightly confused about the purpose of the RF (radiofrequency) pulse in NMR. The powerpoint of my course mentioned that an RF pulse perturbs the equilibrium magnetization and sets the nucleus ...
JeyDean G's user avatar
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39 views

Is there any summary of cavity QED and spin resonance related effects and splittings?

I recently started working on NMR-based qubits and I have lots of confusion regarding the definitions of different interactions and energy level splitting phenomenon. I wonder if you know any ...
0 votes
1 answer
81 views

At what power of magnetic resonance does metal embedded in a person start to be pulled?

What is the level (number) of magnetic resonance necessary to provide an unsafe environment for a person who has metal embedded in their upper body? At what level do the metal shards start to be ...
gsmckee0740's user avatar
2 votes
2 answers
136 views

NMR/EPR with an RF electric field

Is it possible to perform NMR/EPR spin alignment with an oscillating electric field instead of a magnetic field (so with a sample inside the RF electric field of capacitive plates rather than a RF ...
Tom's user avatar
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1 answer
686 views

NMR: Why does 180 degree pulse turn around direction of lamor precession?

In descriptions of the spin echo measurement sequence, it says first a $90°$ pulse turns the magnetization sum vector into the transversal plane where it rotates with the Larmor frequency spins of ...
mcExchange's user avatar
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1 answer
757 views

Why gyromagnetic ratios of different nuclei are different?

I have recently started reading about NMR spectroscopy. I know the formula $\mu$ = $\gamma.J$, where J is the angular momentum (intrinsic or spin angular momentum) of the particle. I also know the $\...
user avatar
2 votes
0 answers
17 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 ...
C-Consciousness's user avatar
5 votes
3 answers
90 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 ...
S.G.'s user avatar
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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"?
Evamentality's user avatar