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相关概念视频

NMR Spectrometers: Resolution and Error Correction01:14

NMR Spectrometers: Resolution and Error Correction

683
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...
683
Carbon-13 (¹³C) NMR: Overview01:10

Carbon-13 (¹³C) NMR: Overview

5.6K
Carbon-13 is a naturally occurring NMR-active isotope of carbon with a low natural abundance of 1.1%. In contrast, carbon-12 is the most abundant isotope of carbon with zero nuclear spin. Therefore, it is NMR inactive. The gyromagnetic ratio of carbon-13 is smaller than that of protons. As a result, carbon-13 resonance is about 6000 times weaker than proton resonance. For a given magnetic field strength, the resonance frequency of carbon-13 is about one-fourth of the resonance frequency for...
5.6K
¹³C NMR: ¹H–¹³C Decoupling01:04

¹³C NMR: ¹H–¹³C Decoupling

1.1K
The probability of having two carbon-13 atoms next to each other is negligible because of the low natural abundance of carbon-13. Consequently, peak splitting due to carbon-carbon spin-spin coupling is not observed in spectra. However, protons up to three sigma bonds away split the carbon signal according to the n+1 rule, resulting in complicated spectra.
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
1.1K
Atomic Nuclei: Magnetic Resonance01:05

Atomic Nuclei: Magnetic Resonance

644
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...
644
Other Nuclides: 31P, 19F, 15N NMR01:16

Other Nuclides: 31P, 19F, 15N NMR

376
Many organic, inorganic, and biological molecules contain spin-half nuclei such as nitrogen-15, fluorine-19, and phosphorus-31. As a result, NMR studies of these nuclei have found extensive applications in chemical and biological research.
While fluorine-19 and phosphorous-31 have high natural abundances (100%) and positive gyromagnetic ratios, nitrogen-15 has a low natural abundance and a negative gyromagnetic ratio. However, nitrogen-15 is still preferred over nitrogen-14 (which has a...
376
Atomic Nuclei: Nuclear Spin State Population Distribution01:14

Atomic Nuclei: Nuclear Spin State Population Distribution

971
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
971

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相关实验视频

Updated: Jun 21, 2025

High-Sensitivity Nuclear Magnetic Resonance at Giga-Pascal Pressures: A New Tool for Probing Electronic and Chemical Properties of Condensed Matter under Extreme Conditions
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固态NMR13C在高磁场时的灵敏度.

Ruixian Han1, Collin G Borcik2, Songlin Wang3

  • 1Department of Chemistry, University of Wisconsin-Madison, Madison, WI, United States.

Journal of magnetic resonance (San Diego, Calif. : 1997)
|July 11, 2024
PubMed
概括

核磁共振 (NMR) 实验中的更高磁场可以提高信号噪声比 (SNR). 这项研究量化了探针设计和磁场强度 (B0) 的SNR增益,为原始和质量有限的灵敏度找到最佳配置.

关键词:
(13)C检测检测的方法高磁场的高磁场的磁场.在SSNMR中,MAS是SSNMR中的一个.探测器设计设计敏感度 敏感度 敏感度

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科学领域:

  • 核磁共振 (NMR) 光谱学 核磁共振 (NMR) 光谱学
  • 分析化学 分析化学
  • 材料科学 材料科学 材料科学

背景情况:

  • 在核磁共振 (NMR) 实验中,灵敏度至关重要.
  • 预计信号噪声比 (SNR) 随着静态磁场 (B0) 的增加而增加.
  • 了解探头设计和B0依赖性对于最大化SNR至关重要.

研究的目的:

  • 在一系列磁场 (14.1至21.1 T) 中,在魔法角度旋转 (MAS) 下系统地研究13C SNR.
  • 评估不同的NMR探头设计和转子尺寸对SNR的影响.
  • 为了建立B0,探测器特征和SNR之间的定量关系.

主要方法:

  • 使用五个光谱仪在17个探测器配置中进行了24个测量集.
  • 采用N-乙瓦林作为主要标准,与阿达曼坦,甘氨酸,六甲基和3-甲基酸进行比较.
  • 系统地改变了转子尺寸 (1.6,2.5和3.2毫米) 和磁场强度.

主要成果:

  • 最佳的原始SNR是通过在17.6T的平衡3.2毫米探头设计获得的.
  • 最好的质量限制SNR是使用平衡的1.6毫米探头设计在21.1T时获得的.
  • 在21.1T时,旋转器尺寸增加到2.5mm以上,原始SNR的回报率下降.

结论:

  • 该研究提供了对探测器效率,接收器噪声和B0依赖的SNR贡献的全面了解.
  • 在高磁场下,特定的探头设计和转子尺寸是不同SNR指标 (原始与质量有限) 的最佳选择.
  • 这些发现指导了NMR探针的选择和优化,以提高高场NMR的灵敏度.