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NMR Simple Explanation

By Applied Electronics - Saturday, October 29, 2016 No Comments
Here a simple explanation of NMR is given. NMR is shortform for Nuclear Magnetic Resonance and is a name derived from a physical phenomenon in which a particle at atomic scale shows resonance with external applied magnetic field.

To explain NMR consider a sample containing approximately 10 to the power 23 atoms and each atom contains nucleus with surrounding electrons. The nucleus has neutron and protons particles. At room temperature, the spins of the protons are randomly oriented without any preferred direction. The magnetic property of the proton is via the spin angular momentum which is related to the magnetic moment. At room temperature, the spins are randomly oriented which means that the magnetic moments are randomly oriented. When such sample is placed inside a static magnetic field then higher proportional proton align with the external static magnetic field and we get a net magnetic moment along the direction of the externally applied static magnetic field. This net magnetic moment is called magnetization.


The explain further in details see the following simple figure- a NMR tube with a liquid sample and the random spins of nucleus.

NMR Simple Explanation 1
Now when the sample tube is placed inside a static magnetic field the spins orients themselves more or less along the external magnetic field as shown in the following figure.

NMR Simple Explanation 2


Quantum mechanically each spin is not stationary but precesses about their own axis. This gives rise to spin angular momentum or magnetic moment of the particle. The frequency of precession is called Larmor frequency or the resonant frequency of the spinning particle due to the externally applied magnetic field. Hope this was useful and simple enough for understanding what is NMR.

NMR Simple Explanation 3

The whole experiment which utilizes this resonance phenomenon of quantum mechanical particle or atomic particles is called Nuclear Magnetic Resonance experiments.

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