Questions tagged [nuclear-magnetic-resonance]

For questions about Nuclear Magnetic Resonance

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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 (...
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Hypothetical NMR experiment

Say I set the RF of NMR to resonate to a specific frequency of a specific isotope of nitrogen, based on the magnetic field strength of the NMR machine, Now, imagine if I had put in egg whites(or any ...
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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, ...
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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 ...
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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 ...
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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 ...
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Can electron paramagnetic resonance occur in the low megahertz range?

My understanding was that EPR can occur in certain energy bands (and thus at certain magnetic field strengths). Is it the case that it is limited to those energy levels and if so, is there any in the ...
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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 ...
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NMR Remote sensing - how does it work?

I was watching https://www.youtube.com/watch?v=xdZ3bQRLn0w Generally - you can activate use a strong magnetic field on ground, perturb it, and the pick the signal up with a satellite. The result would ...
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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 ...
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Nuclear spin and angular momentum

Could someone explain the relationship 1.3? I thought that in nuclear physics the spin and angular momentum can be used interchangably?
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How to generate a Hadamard Gate in Spin 1 NMR?

I am studying about the gate controllability of Spin 1 systems and I would like make a Hadamard gate using only X,Y rotations and the offset. I want to do this without invoking techniques for making ...
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Dynamical decoupling using the Waugh-Huber-Haeberlen (WaHuHa) pulse sequence

I am trying to simulate the coherence profile of an interacting system of spin-1/2 particles after applying the WAHUHA pulse sequence. The system considered is a 1D spin chain with only nearest-...
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Intuition behind residence times measurement through NMR

I have read that residence times of molecules near to other molecules can be obtained trough NMR experiments. For example, the average time that a average water molecule stay close to a protein. In ...
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What does it mean that some NMR spectroscopy data is not phase sensitive?

What does it mean if we say that NMR spectroscopy is not usually phase sensitive? And why is this no sensitivity to phase happening?
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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 $\...
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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 ...
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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 ...
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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"?
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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{...
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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 ...
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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, ...
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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, ...
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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 ...
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$j$-$j$ 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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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
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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 ...
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1 answer
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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 ...
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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 ...
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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 (...
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1 answer
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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 ...
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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 ...
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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 (...
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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 ...
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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 $\pi/2$-$\pi$ ...
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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 ...
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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 ...
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1 answer
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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 ...
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3 votes
1 answer
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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 ...
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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) + ...
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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: ...
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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 {...
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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 ...
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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 ...
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