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NMR Spectrometers: Overview

NMR Spectrometers: Overview

NMR spectrometers consist of a strong magnet, a radiofrequency transmitter, and a detector attached to a computer console for recording spectra of samples containing NMR-active nuclei. In first-generation NMR instruments called continuous-wave spectrometers, the resonance frequencies of the nuclei are determined by frequency-sweep or field-sweep methods. The magnetic field strength is fixed and the rf signal is swept in the former, while the radiofrequency signal is fixed and the magnetic field...

NMR Spectrometers: Radiofrequency Pulses and Pulse Sequences

NMR Spectrometers: Radiofrequency Pulses and Pulse Sequences

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.

Two-Dimensional (2D) NMR: Overview

Two-Dimensional (2D) NMR: Overview

The 1D NMR spectrum of large and complex molecules like natural products has complicated splitting patterns and overlapping signals, which can be easily interpreted using 2-dimensional (2D) NMR. Unlike 1D NMR, 2D NMR has two frequency axes that provide the coupling information between the nucleus A and nucleus B in a molecule. The process from which 2D spectra are obtained has four steps.
The first step is the preparation period, during which nucleus A is excited with a radiofrequency pulse.

¹H NMR: Interpreting Distorted and Overlapping Signals

¹H NMR: Interpreting Distorted and Overlapping Signals

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 slanted or...

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Related Experiment Video

Updated: May 28, 2026

Simultaneous Data Collection of fMRI and fNIRS Measurements Using a Whole-Head Optode Array and Short-Distance Channels

Simultaneous Data Collection of fMRI and fNIRS Measurements Using a Whole-Head Optode Array and Short-Distance Channels

Published on: October 20, 2023

Functional spectroscopy to no-gradient fMRI.

Jürgen Hennig¹

¹Dept.of Radiology, University Medical Center, Breisacherst.60a, 79106 Freiburg, Germany. juergen.hennig@uniklinik-freiburg.de

|October 18, 2011

Summary

This summary is machine-generated.

This article reviews functional magnetic resonance imaging (fMRI) history, from early functional spectroscopy and the initial dip discovery to modern gradient-less MR-encephalography (MREG). It highlights the innovation driving these advancements in brain imaging.

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Simultaneous Data Collection of fMRI and fNIRS Measurements Using a Whole-Head Optode Array and Short-Distance Channels

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Published on: October 20, 2023

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Area of Science:

Neuroimaging
Biophysics
Medical Physics

Background:

The article traces the evolution of functional magnetic resonance imaging (fMRI).
It covers early functional spectroscopy techniques and recent gradient-less imaging methods.

Observation:

The initial dip in functional spectroscopy was a key early observation.
MR-encephalography (MREG) represents a recent advancement in gradient-less imaging.

Findings:

The study details the development of functional spectroscopy and the detection of the initial dip.
It presents the principles and applications of gradient-less MR-encephalography (MREG).

Implications:

These advancements in fMRI offer new insights into brain function and activity.
Understanding the historical development of these techniques inspires future neuroimaging research.