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Principles of Nuclear Magnetic Resonance
How Electron Density Shields Nuclei in NMR
Description
Electron density around a nucleus affects how strongly it is shielded in NMR spectroscopy. When an applied magnetic field acts on a molecule, the electrons begin to circulate. This creates a local diamagnetic current within the molecule.
The circulating sigma-bonding electrons produce a local mag...
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Transcript
在分子中，外加磁场B0，导致原子核周围的电子密度发生流动，形成局部抗磁性电流，从而产生局部磁场， B局部，相反 B0.
因此，这些原子核所感受到的有效磁场 Beffective 等于 B0 减去 Blocal，这一现象称为局部抗磁屏蔽。
本质上，Blocal 随着原子核周围电子密度的增加而增大，导致屏蔽效应增强，Beffective 降低。
由于分...
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