JoVE Logo

サインイン

7.8 : Atomic Nuclei: Nuclear Relaxation Processes

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 to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis, the precessing magnetic moments are randomly oriented around the z-axis. This results in a net magnetization, M, along the z-axis, with no net contribution from the transverse components on the xy plane.

Upon excitation with radiofrequency radiation, the nuclei absorb energy, and the excited spins acquire some coherence. It follows that Mx and My are no longer zero, Mz decreases, and the net magnetization, M, tips toward the y-axis. Upon continued excitation, the population difference between the spin states can decrease, along with the signal intensity. This is called saturation.

Eventually, the excited nuclear spins return to the equilibrium state through a process called relaxation. During relaxation, the xy coherence disappears, and the net magnetization is restored to the equilibrium value along the z-axis.

タグ

Atomic NucleiNuclear Relaxation ProcessesNuclear Spin StatesMagnetic FieldPrecessionMagnetizationRadiofrequency RadiationCoherenceSaturationEquilibrium StateRelaxation Process

章から 7:

article

Now Playing

7.8 : Atomic Nuclei: Nuclear Relaxation Processes

Principles of Nuclear Magnetic Resonance

603 閲覧数

article

7.1 : Nuclear Magnetic Resonance (NMR): Overview

Principles of Nuclear Magnetic Resonance

2.1K 閲覧数

article

7.2 : Atomic Nuclei: Nuclear Spin

Principles of Nuclear Magnetic Resonance

1.6K 閲覧数

article

7.3 : Atomic Nuclei: Nuclear Magnetic Moment

Principles of Nuclear Magnetic Resonance

1.0K 閲覧数

article

7.4 : Atomic Nuclei: Nuclear Spin State Overview

Principles of Nuclear Magnetic Resonance

848 閲覧数

article

7.5 : Atomic Nuclei: Nuclear Spin State Population Distribution

Principles of Nuclear Magnetic Resonance

918 閲覧数

article

7.6 : Atomic Nuclei: Larmor Precession Frequency

Principles of Nuclear Magnetic Resonance

1.1K 閲覧数

article

7.7 : Atomic Nuclei: Magnetic Resonance

Principles of Nuclear Magnetic Resonance

605 閲覧数

article

7.9 : Atomic Nuclei: Types of Nuclear Relaxation

Principles of Nuclear Magnetic Resonance

239 閲覧数

article

7.10 : NMR Spectrometers: Overview

Principles of Nuclear Magnetic Resonance

1.0K 閲覧数

article

7.11 : NMR Spectrometers: Radiofrequency Pulses and Pulse Sequences

Principles of Nuclear Magnetic Resonance

732 閲覧数

article

7.12 : NMR Spectrometers: Resolution and Error Correction

Principles of Nuclear Magnetic Resonance

652 閲覧数

article

7.13 : Diamagnetic Shielding of Nuclei: Local Diamagnetic Current

Principles of Nuclear Magnetic Resonance

814 閲覧数

JoVE Logo

個人情報保護方針

利用規約

一般データ保護規則

研究

教育

JoVEについて

Copyright © 2023 MyJoVE Corporation. All rights reserved