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Chapter 7

Principles of Nuclear Magnetic Resonance

核磁共振 (NMR):概述
核磁共振 (NMR):概述
Nuclear magnetic resonance (NMR) is a phenomenon exhibited by certain nuclei that can absorb characteristic radio frequency radiation under certain ...
原子核:核自旋
原子核:核自旋
All atomic particles possess an intrinsic angular momentum, or 'spin'. Electrons, protons, and neutrons each have a spin value of ½, although ...
原子核:核磁矩
原子核:核磁矩
All atomic nuclei are positively charged. When they have a nonzero spin, they behave like rotating charges. As a consequence of their charge and spin, ...
原子核:核自旋态概述
原子核:核自旋态概述
NMR-active nuclei have energy levels called 'spin states' that are associated with the orientations of their nuclear magnetic moments. In the ...
原子核:核自旋态种群分布
原子核:核自旋态种群分布
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 ...
原子核:Larmor 岁差频率
原子核:Larmor 岁差频率
The earth's gravitational field produces a 'twisting force' perpendicular to the angular momentum of a spinning mass (such as a spinning top) ...
原子核:磁共振
原子核:磁共振
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 ...
原子核:核弛豫过程
原子核:核弛豫过程
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin ...
原子核:核弛豫的类型
原子核:核弛豫的类型
Relaxation in NMR systems is a first-order exponential decay and can occur by either spin–lattice or spin–spin mechanisms. Spin–lattice ...
NMR 波谱仪:概述
NMR 波谱仪:概述
NMR spectrometers consist of a strong magnet, a radiofrequency transmitter, and a detector attached to a computer console for recording spectra of samples ...
核磁共振波谱仪:射频脉冲和脉冲序列
核磁共振波谱仪:射频脉冲和脉冲序列
A pulse is a short burst of radio waves distributed over a range of frequencies that simultaneously excites all the nuclei in the sample. Upon passing a ...
NMR 波谱仪:分辨率和误差校正
NMR 波谱仪:分辨率和误差校正
When magnetic nuclei in a sample achieve resonance and undergo relaxation, the signal detected in NMR is an approximately exponential free induction ...
原子核的抗磁屏蔽:局部抗磁电流
原子核的抗磁屏蔽:局部抗磁电流
An applied magnetic field causes the electrons present in the molecule to circulate, setting up a local diamagnetic current within the molecule. The local ...
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