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相关概念视频

Spin–Spin Coupling Constant: Overview01:08

Spin–Spin Coupling Constant: Overview

854
In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must...
854
Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)01:20

Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)

918
Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
918
Chirality at Nitrogen, Phosphorus, and Sulfur02:30

Chirality at Nitrogen, Phosphorus, and Sulfur

5.6K
Chirality is most prevalent in carbon-based tetrahedral compounds, but this important facet of molecular symmetry extends to sp3-hybridized nitrogen, phosphorus and sulfur centers, including trivalent molecules with lone pairs. Here, the lone pair behaves as a functional group in addition to the other three substituents to form an analogous tetrahedral center that can be chiral.
A consequence of chirality is the need for enantiomeric resolution. While this is theoretically possible for all...
5.6K
Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)01:22

Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)

1.0K
Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the...
1.0K
2D NMR: Heteronuclear Single-Quantum Correlation Spectroscopy (HSQC)01:19

2D NMR: Heteronuclear Single-Quantum Correlation Spectroscopy (HSQC)

588
Heteronuclear single-quantum correlation spectroscopy (HSQC) is a 2D NMR technique that reveals one-bond correlations between hydrogen and a heteronucleus. The HSQC experiment is similar to the heteronuclear correlation experiment (HETCOR) but is more sensitive. In the HSQC spectrum, the proton chemical shift is plotted on the horizontal F2 axis, while the 13C chemical shift is plotted on the vertical F1 axis. The corresponding proton and 13C spectra are also shown. The HSQC contour plot does...
588
¹H NMR: Interpreting Distorted and Overlapping Signals01:02

¹H NMR: Interpreting Distorted and Overlapping Signals

937
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are...
937

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在二维磁铁CrSBr中以旋转奇拉力驱动的第二和生成.

Dezhao Wu1, Yong Xu1,2,3, Meng Ye4

  • 1State Key Laboratory of Low Dimensional Quantum Physics and, Department of Physics, Tsinghua University, Beijing 100084, China.

Science advances
|April 4, 2025
PubMed
概括
此摘要是机器生成的。

研究人员在反铁磁材料中发现了一种新的可调光学现象,即性第二生成 (SHG). 这一发现增强了先进光学设备和磁电检测的潜力.

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科学领域:

  • 凝聚物质物理学 凝聚物质物理学
  • 光学是什么?光学是什么?光学是什么?
  • 材料科学 材料科学 材料科学

背景情况:

  • 磁性和光呈现复杂的相互作用,导致各种光学现象.
  • 磁化诱导的第二和生成 (MSHG) 是这种相互作用中的一个关键现象.
  • 抗铁磁 (AFM) 材料为探索新的光学效应提供了独特的特性.

研究的目的:

  • 为了证明MSHG的新型形式,由矢量旋转性产生的,称为性第二和生成 (SHG).
  • 调查 AFM 材料中的 chiral SHG 的可调性和物理机制.
  • 探索这种现象在光学设备和磁电检测中的潜在应用.

主要方法:

  • 抗铁磁 (AFM) CrSBr双层系统的理论建模.
  • 研究旋转倾斜对第二和生成 (SHG) 信号的影响.
  • 分析旋转性,电极化和MSHG之间的关系.

主要成果:

  • 在AFM CrSBr双层中,从向量旋转奇拉性演示出奇拉SHG的出现.
  • 通过旋转倾斜,展示了 chiral SHG 的连续可调性,超过了内在的 MSHG.
  • 鉴定了性SHG (旋转性,极化) 和内在MSHG (尼尔向量) 的独特物理机制.
  • 揭示了SHG信号的显著调节,原因是旋转转向逆转时,奇拉和内在MSHG之间的干扰.

结论:

  • 在反铁磁体中发现了一种独特且高度可调的合性SHG现象.
  • 建立了性SHG作为与内在MSHG截然不同的机制,由旋转性和极化驱动.
  • 强调了先进的AFM光学设备和磁电检测技术的潜力.