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 radio frequency pulse along the x-axis, the nuclei absorb energy corresponding to their Larmor frequencies and achieve resonance. This shifts the net magnetization vector from the z-axis toward the transverse plane. This angle of rotation of the magnetization vector, or the flip angle, is proportional to the duration and intensity of the pulse. A 90° pulse shifts the net magnetization precisely onto the x-y plane, while a 180° pulse shifts it to the −z direction.

Pulses are applied in sequences to reveal detailed information about the sample under study. A simple pulse sequence begins with an excitation pulse from the transmitter, followed by an acquisition time during which the free induction decay signals are collected and digitized by the computer console. The nuclei relax and reestablish equilibrium before the next pulse is applied in the ensuing relaxation delay.

Tags
NMR SpectrometersRadiofrequency PulsesPulse SequencesLarmor FrequenciesResonanceMagnetization VectorFlip AngleExcitation PulseFree Induction DecayRelaxation DelayEnergy AbsorptionSample Analysis

From Chapter 7:

article

Now Playing

7.11 : NMR Spectrometers: Radiofrequency Pulses and Pulse Sequences

Principles of Nuclear Magnetic Resonance

619 Views

article

7.1 : Nuclear Magnetic Resonance (NMR): Overview

Principles of Nuclear Magnetic Resonance

1.6K Views

article

7.2 : Atomic Nuclei: Nuclear Spin

Principles of Nuclear Magnetic Resonance

1.3K Views

article

7.3 : Atomic Nuclei: Nuclear Magnetic Moment

Principles of Nuclear Magnetic Resonance

885 Views

article

7.4 : Atomic Nuclei: Nuclear Spin State Overview

Principles of Nuclear Magnetic Resonance

732 Views

article

7.5 : Atomic Nuclei: Nuclear Spin State Population Distribution

Principles of Nuclear Magnetic Resonance

828 Views

article

7.6 : Atomic Nuclei: Larmor Precession Frequency

Principles of Nuclear Magnetic Resonance

844 Views

article

7.7 : Atomic Nuclei: Magnetic Resonance

Principles of Nuclear Magnetic Resonance

541 Views

article

7.8 : Atomic Nuclei: Nuclear Relaxation Processes

Principles of Nuclear Magnetic Resonance

548 Views

article

7.9 : Atomic Nuclei: Types of Nuclear Relaxation

Principles of Nuclear Magnetic Resonance

174 Views

article

7.10 : NMR Spectrometers: Overview

Principles of Nuclear Magnetic Resonance

863 Views

article

7.12 : NMR Spectrometers: Resolution and Error Correction

Principles of Nuclear Magnetic Resonance

541 Views

article

7.13 : Diamagnetic Shielding of Nuclei: Local Diamagnetic Current

Principles of Nuclear Magnetic Resonance

721 Views

JoVE Logo

Privacy

Terms of Use

Policies

Research

Education

ABOUT JoVE

Copyright © 2025 MyJoVE Corporation. All rights reserved