nmr Definition and Topics - 58 Discussions

Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are perturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with a frequency characteristic of the magnetic field at the nucleus. This process occurs near resonance, when the oscillation frequency matches the intrinsic frequency of the nuclei, which depends on the strength of the static magnetic field, the chemical environment, and the magnetic properties of the isotope involved; in practical applications with static magnetic fields up to ca. 20 tesla, the frequency is similar to VHF and UHF television broadcasts (60–1000 MHz). NMR results from specific magnetic properties of certain atomic nuclei. Nuclear magnetic resonance spectroscopy is widely used to determine the structure of organic molecules in solution and study molecular physics and crystals as well as non-crystalline materials. NMR is also routinely used in advanced medical imaging techniques, such as in magnetic resonance imaging (MRI).
The most commonly used nuclei are 1H and 13C, although isotopes of many other elements can be studied by high-field NMR spectroscopy as well. In order to interact with the magnetic field in the spectrometer, the nucleus must have an intrinsic nuclear magnetic moment and angular momentum. This occurs when an isotope has a nonzero nuclear spin, meaning an odd number of protons and/or neutrons (see Isotope). Nuclides with even numbers of both have a total spin of zero and are therefore NMR-inactive.
A key feature of NMR is that the resonance frequency of a particular sample substance is usually directly proportional to the strength of the applied magnetic field. It is this feature that is exploited in imaging techniques; if a sample is placed in a non-uniform magnetic field then the resonance frequencies of the sample's nuclei depend on where in the field they are located. Since the resolution of the imaging technique depends on the magnitude of the magnetic field gradient, many efforts are made to develop increased gradient field strength.
The principle of NMR usually involves three sequential steps:

The alignment (polarization) of the magnetic nuclear spins in an applied, constant magnetic field B0.
The perturbation of this alignment of the nuclear spins by a weak oscillating magnetic field, usually referred to as a radio-frequency (RF) pulse. The oscillation frequency required for significant perturbation is dependent upon the static magnetic field (B0) and the nuclei of observation.
The detection of the NMR signal during or after the RF pulse, due to the voltage induced in a detection coil by precession of the nuclear spins around B0. After an RF pulse, precession usually occurs with the nuclei's intrinsic Larmor frequency and, in itself, does not involve transitions between spin states or energy levels.The two magnetic fields are usually chosen to be perpendicular to each other as this maximizes the NMR signal strength. The frequencies of the time-signal response by the total magnetization (M) of the nuclear spins are analyzed in NMR spectroscopy and magnetic resonance imaging. Both use applied magnetic fields (B0) of great strength, often produced by large currents in superconducting coils, in order to achieve dispersion of response frequencies and of very high homogeneity and stability in order to deliver spectral resolution, the details of which are described by chemical shifts, the Zeeman effect, and Knight shifts (in metals). The information provided by NMR can also be increased using hyperpolarization, and/or using two-dimensional, three-dimensional and higher-dimensional techniques.
NMR phenomena are also utilized in low-field NMR, NMR spectroscopy and MRI in the Earth's magnetic field (referred to as Earth's field NMR), and in several types of magnetometers.

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  1. Athenian

    Finding the Magnetic Field (B_0) on a Graph [NMR]

    Background Information (Not Strictly Necessary): As a quick recap, the graph I am dealing with is a semi-logarithmic graph of free induction decay (FID) amplitude as a function of time. To acquire the value for ##{T_2}^*## (and its uncertainty) in the graph, I used the below equation to do so...
  2. Athenian

    Calculating Numerical Uncertainties in an Equation

    Background Information: I am working on a pulsed NMR lab project that involves graphing out a semi-log graph of free induction decay amplitude as a function of time. After graphing out the semi-log graph, I am to determine the apparent spin-spin relaxation time (##{T_2}^*##) through the...
  3. Athenian

    Spin-Lattice and Spin-Spin Relaxation Time Question

    Please refer to the homework statement. Or, if one would like to put it in other words, how would I go about finding ##T_2## if I know the delay time between 90-degree and 180-degree pulses? Is there an equation that helps solve this succinctly?
  4. Christoffer B

    Imperfections in magnet pole pieces

    Hi all, I'm fairly new here. I'm currently designing an as-homogene-as-possible permanent magnet for low-field NMR and similar experiments. I'm on a fairly tight budget, and having finally found pole pieces for my magnets, I got them even though they have a small saw cut in the edge. approx. 5...
  5. W

    Relation between magnetism and material creep

    Hello, I am a civil engineer and have been working on concrete creep phenomenon for several years now. After reviewing a large amount of literature on related topics throughout this time, some interesting observations have emerged, and they have formed the idea that the material creep mechanism...
  6. Javier Lopez

    I What are the magnetic states of nucleons?

    Could I have hundred times the ground state or there is a limit? Is there a limit for excited magnetic momentum that if reached the nucleous explode or generate gammas? I suppose If I excite it it would spin faster but proportional to quantum values. Note: there is a "theory" to avoid electron...
  7. HastiM

    Imaging Carbon C 14 by NMR

    Homework Statement We want to image carbon C14 atoms using NMR with magnetic field of B=3 T. What frequency do we need to use? Use the following facts: C14 has 0% abundance, nuclear spin of I=3 and g=0.273 Homework Equations The frequency is given by f= (2⋅I) ⋅ (g ⋅B ⋅μ)/(1836 ⋅h), where μ...
  8. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 1: Introduction to NMR spectroscopy

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 1: Introduction to NMR spectroscopy

    All copyright strictly reserved to Prof. Atreya and NPTEL, Govt. of India. COURSE WEBSITE: https://www.youtube.com/redirect?redir_token=J3W-BvVF9P_QSjr1ljVg8I2O_Bl8MTUyNDU4NDYyMEAxNTI0NDk4MjIw&event=playlist_description&q=http%3A%2F%2Fwww.nptel.ac.in%2Fcourses%2F104108078%2F10
  9. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 2: The alignment of nuclear spins in presence of magnetic field

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 2: The alignment of nuclear spins in presence of magnetic field

    All copyright strictly reserved to Prof. Atreya and NPTEL, Govt. of India. COURSE WEBSITE: https://www.youtube.com/redirect?redir_token=J3W-BvVF9P_QSjr1ljVg8I2O_Bl8MTUyNDU4NDYyMEAxNTI0NDk4MjIw&event=playlist_description&q=http%3A%2F%2Fwww.nptel.ac.in%2Fcourses%2F104108078%2F10
  10. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 3: Introduction to rotating frame

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 3: Introduction to rotating frame

    All copyright strictly reserved to Prof. Atreya and NPTEL, Govt. of India. COURSE WEBSITE: https://www.youtube.com/redirect?redir_token=J3W-BvVF9P_QSjr1ljVg8I2O_Bl8MTUyNDU4NDYyMEAxNTI0NDk4MjIw&event=playlist_description&q=http%3A%2F%2Fwww.nptel.ac.in%2Fcourses%2F104108078%2F10
  11. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 4: Introduction to rotating frame

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 4: Introduction to rotating frame

    All copyright strictly reserved to Prof. Atreya and NPTEL, Govt. of India. COURSE WEBSITE: https://www.youtube.com/redirect?redir_token=J3W-BvVF9P_QSjr1ljVg8I2O_Bl8MTUyNDU4NDYyMEAxNTI0NDk4MjIw&event=playlist_description&q=http%3A%2F%2Fwww.nptel.ac.in%2Fcourses%2F104108078%2F10
  12. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 5: NMR Hardware

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 5: NMR Hardware

    All copyright strictly reserved to Prof. Atreya and NPTEL, Govt. of India. COURSE WEBSITE: https://www.youtube.com/redirect?redir_token=J3W-BvVF9P_QSjr1ljVg8I2O_Bl8MTUyNDU4NDYyMEAxNTI0NDk4MjIw&event=playlist_description&q=http%3A%2F%2Fwww.nptel.ac.in%2Fcourses%2F104108078%2F10
  13. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 6: The concept of chemical shift

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 6: The concept of chemical shift

    All copyright strictly reserved to Prof. Atreya and NPTEL, Govt. of India. COURSE WEBSITE: https://www.youtube.com/redirect?redir_token=J3W-BvVF9P_QSjr1ljVg8I2O_Bl8MTUyNDU4NDYyMEAxNTI0NDk4MjIw&event=playlist_description&q=http%3A%2F%2Fwww.nptel.ac.in%2Fcourses%2F104108078%2F10
  14. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 7: Factors that affect chemical shifts

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 7: Factors that affect chemical shifts

    All copyright strictly reserved to Prof. Atreya and NPTEL, Govt. of India. COURSE WEBSITE: https://www.youtube.com/redirect?redir_token=J3W-BvVF9P_QSjr1ljVg8I2O_Bl8MTUyNDU4NDYyMEAxNTI0NDk4MjIw&event=playlist_description&q=http%3A%2F%2Fwww.nptel.ac.in%2Fcourses%2F104108078%2F10
  15. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 8: Chemical shift referencing

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 8: Chemical shift referencing

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  16. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 9: J- coupling

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 9: J- coupling

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  17. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 10: Recap of basics

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 10: Recap of basics

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  18. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 11: Introduction to general one dimensional NMR experiment

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 11: Introduction to general one dimensional NMR experiment

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  19. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 12: Practical aspects of recording a 1D NMR experiment I

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 12: Practical aspects of recording a 1D NMR experiment I

    All copyright strictly reserved to Prof. Atreya and NPTEL, Govt. of India. COURSE WEBSITE: https://www.youtube.com/redirect?redir_token=J3W-BvVF9P_QSjr1ljVg8I2O_Bl8MTUyNDU4NDYyMEAxNTI0NDk4MjIw&event=playlist_description&q=http%3A%2F%2Fwww.nptel.ac.in%2Fcourses%2F104108078%2F10
  20. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 13: Practical aspects of recording a 1D NMR experiment II

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 13: Practical aspects of recording a 1D NMR experiment II

    All copyright strictly reserved to Prof. Atreya and NPTEL, Govt. of India. COURSE WEBSITE: https://www.youtube.com/redirect?redir_token=J3W-BvVF9P_QSjr1ljVg8I2O_Bl8MTUyNDU4NDYyMEAxNTI0NDk4MjIw&event=playlist_description&q=http%3A%2F%2Fwww.nptel.ac.in%2Fcourses%2F104108078%2F10
  21. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 14: Practical aspects of recording a 1D NMR experiment III

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 14: Practical aspects of recording a 1D NMR experiment III

    All copyright strictly reserved to Prof. Atreya and NPTEL, Govt. of India. COURSE WEBSITE: https://www.youtube.com/redirect?redir_token=J3W-BvVF9P_QSjr1ljVg8I2O_Bl8MTUyNDU4NDYyMEAxNTI0NDk4MjIw&event=playlist_description&q=http%3A%2F%2Fwww.nptel.ac.in%2Fcourses%2F104108078%2F10
  22. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 15: NMR Data processing

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 15: NMR Data processing

    All copyright strictly reserved to Prof. Atreya and NPTEL, Govt. of India. COURSE WEBSITE: https://www.youtube.com/redirect?redir_token=J3W-BvVF9P_QSjr1ljVg8I2O_Bl8MTUyNDU4NDYyMEAxNTI0NDk4MjIw&event=playlist_description&q=http%3A%2F%2Fwww.nptel.ac.in%2Fcourses%2F104108078%2F10
  23. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 16: Basic aspects of 1D proton NMR analysis

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 16: Basic aspects of 1D proton NMR analysis

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  24. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 17: Analysis of an example 1D proton spectrum

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 17: Analysis of an example 1D proton spectrum

    All copyright strictly reserved to Prof. Atreya and NPTEL, Govt. of India. COURSE WEBSITE: https://www.youtube.com/redirect?redir_token=J3W-BvVF9P_QSjr1ljVg8I2O_Bl8MTUyNDU4NDYyMEAxNTI0NDk4MjIw&event=playlist_description&q=http%3A%2F%2Fwww.nptel.ac.in%2Fcourses%2F104108078%2F10
  25. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 18: Analysis of 1D 1H NMR spectra of molecules I

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 18: Analysis of 1D 1H NMR spectra of molecules I

    All copyright strictly reserved to Prof. Atreya and NPTEL, Govt. of India. COURSE WEBSITE: https://www.youtube.com/redirect?redir_token=J3W-BvVF9P_QSjr1ljVg8I2O_Bl8MTUyNDU4NDYyMEAxNTI0NDk4MjIw&event=playlist_description&q=http%3A%2F%2Fwww.nptel.ac.in%2Fcourses%2F104108078%2F10
  26. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 19: Analysis of 1D 1H NMR spectra of molecules II

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 19: Analysis of 1D 1H NMR spectra of molecules II

    All copyright strictly reserved to Prof. Atreya and NPTEL, Govt. of India. COURSE WEBSITE: https://www.youtube.com/redirect?redir_token=J3W-BvVF9P_QSjr1ljVg8I2O_Bl8MTUyNDU4NDYyMEAxNTI0NDk4MjIw&event=playlist_description&q=http%3A%2F%2Fwww.nptel.ac.in%2Fcourses%2F104108078%2F10
  27. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 20: 1D 13C NMR

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 20: 1D 13C NMR

    All copyright strictly reserved to Prof. Atreya and NPTEL, Govt. of India. COURSE WEBSITE: https://www.youtube.com/redirect?redir_token=J3W-BvVF9P_QSjr1ljVg8I2O_Bl8MTUyNDU4NDYyMEAxNTI0NDk4MjIw&event=playlist_description&q=http%3A%2F%2Fwww.nptel.ac.in%2Fcourses%2F104108078%2F10
  28. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 21: Why do we need 2D NMR

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 21: Why do we need 2D NMR

    All copyright strictly reserved to Prof. Atreya and NPTEL, Govt. of India. COURSE WEBSITE: https://www.youtube.com/redirect?redir_token=J3W-BvVF9P_QSjr1ljVg8I2O_Bl8MTUyNDU4NDYyMEAxNTI0NDk4MjIw&event=playlist_description&q=http%3A%2F%2Fwww.nptel.ac.in%2Fcourses%2F104108078%2F10
  29. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 22: A qualitative explanation of how 2D NMR experiment works

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 22: A qualitative explanation of how 2D NMR experiment works

    All copyright strictly reserved to Prof. Atreya and NPTEL, Govt. of India. COURSE WEBSITE: https://www.youtube.com/redirect?redir_token=J3W-BvVF9P_QSjr1ljVg8I2O_Bl8MTUyNDU4NDYyMEAxNTI0NDk4MjIw&event=playlist_description&q=http%3A%2F%2Fwww.nptel.ac.in%2Fcourses%2F104108078%2F10
  30. NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 23: Principles of 2D COSY and Total correlation spectroscopy (2D TOCSY)

    NMR Spectroscopy by Prof. Hanudatta S. Atreya (NPTEL):- Lecture 23: Principles of 2D COSY and Total correlation spectroscopy (2D TOCSY)

    All copyright strictly reserved to Prof. Atreya and NPTEL, Govt. of India. COURSE WEBSITE: https://www.youtube.com/redirect?redir_token=J3W-BvVF9P_QSjr1ljVg8I2O_Bl8MTUyNDU4NDYyMEAxNTI0NDk4MjIw&event=playlist_description&q=http%3A%2F%2Fwww.nptel.ac.in%2Fcourses%2F104108078%2F10
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