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Related Concept Videos

Double Resonance Techniques: Overview01:12

Double Resonance Techniques: Overview

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Double resonance techniques in Nuclear Magnetic Resonance (NMR) spectroscopy involve the simultaneous application of two different frequencies or radiofrequency pulses to manipulate and observe two distinct nuclear spins. One important application of double resonance is spin decoupling, which selectively suppresses coupling with one type of nucleus while observing the NMR signal from another nucleus, simplifying the spectrum and enhancing resolution.
Spin decoupling is usually achieved by...
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NMR Spectrometers: Resolution and Error Correction01:14

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When magnetic nuclei in a sample achieve resonance and undergo relaxation, the signal detected in NMR is an approximately exponential free induction decay. Fourier transform of an exponential decay yields a Lorentzian peak in the frequency domain. Lorentzian peaks in an NMR spectrum are defined by their amplitude, full width at half maximum, and position, where the peak width is governed by the spin-spin relaxation time alone. In real experiments, however, the applied magnetic field is rendered...
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NMR Spectroscopy: Spin–Spin Coupling01:08

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The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved...
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¹H NMR Signal Multiplicity: Splitting Patterns01:13

¹H NMR Signal Multiplicity: Splitting Patterns

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When protons A and X are coupled, their nuclear spin energy levels are slightly modified. This is because the energy required to excite proton A to a spin state parallel to proton X is slightly different from the energy required for it to become anti-parallel to spin X. Consequently, there are two possible excitation frequencies for A (A1 and A2), depending on the spin state of X, and vice versa. The mutual nature of coupling implies that the difference between frequencies A1 and A2, indicated...
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Atomic Nuclei: Magnetic Resonance01:05

Atomic Nuclei: Magnetic Resonance

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The number of nuclear spins aligned in the lower energy state is slightly greater than those in the higher energy state. In the presence of an external magnetic field, as the spins precess at the Larmor frequency, the excess population results in a net magnetization oriented along the z axis. When a pulse or a short burst of radio waves at the Larmor frequency is applied along the x axis, the coupling of frequencies causes resonance and flips the nuclear spins of the excess population from the...
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¹H NMR: Long-Range Coupling01:27

¹H NMR: Long-Range Coupling

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The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene...
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Frequency Mixing Magnetic Detection Scanner for Imaging Magnetic Particles in Planar Samples
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Using magnetic coupling to improve multiple resonance NMR probe circuits.

Albert P Zens1

  • 1JEOL, 1101 Library Lane, San Jose, CA 95116, United States.

Journal of Magnetic Resonance (San Diego, Calif. : 1997)
|June 23, 2020
PubMed
Summary

Modern Nuclear Magnetic Resonance (NMR) detectors use multiple resonant circuits for convenience, but this can reduce efficiency. This study shows magnetic coupling in symmetric circuits improves NMR experiment efficiency compared to capacitive coupling.

Keywords:
Circuit fill factorLadder circuitMagnetic couplingMultiple resonanceNMR probeSecondary magnetic coupling

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Area of Science:

  • Nuclear Magnetic Resonance (NMR) Spectroscopy
  • Electrical Engineering
  • Physical Chemistry

Background:

  • Modern NMR detectors offer versatile multi-nuclide resonance capabilities without probe changes.
  • This convenience often leads to a significant loss in experimental efficiency.
  • Improving NMR detector efficiency is crucial for advancing spectroscopic research.

Purpose of the Study:

  • To investigate methods for enhancing the efficiency of multiple resonant NMR circuits.
  • To compare the efficiency of magnetically coupled versus capacitively coupled circuits.
  • To provide a design strategy for more efficient NMR probes.

Main Methods:

  • Analysis of symmetric multiple resonance circuits.
  • Application of magnetic coupling principles.
  • Comparison of circuit efficiencies at 50 Ω ports.
  • Theoretical evaluation of energy transfer in NMR circuits.

Main Results:

  • Magnetically coupled symmetric circuits demonstrate improved efficiency over capacitively coupled designs.
  • The proposed magnetic coupling method enhances signal detection in multi-resonance NMR.
  • Efficiency gains are quantifiable and significant for practical NMR applications.

Conclusions:

  • Symmetric multiple resonance circuits utilizing magnetic coupling offer a superior alternative to capacitive coupling for NMR detectors.
  • This approach mitigates the efficiency loss associated with versatile NMR probes.
  • The findings enable the development of more sensitive and efficient NMR instrumentation.