Magnetic dipole–dipole interaction

Magnetic dipole–dipole interaction

Magnetic dipole–dipole interaction, also called dipolar coupling, refers to the direct interaction between two magnetic dipoles. The potential energy of the interaction is as follows:

 \bold{H} = - \frac{ \mu_0 } {4 \pi r_{jk}^3 } \left( 3 (\bold{m}_j \cdot \bold{e}_{jk})  (\bold{m}_k \cdot \bold{e}_{jk}) - \bold{m}_j \cdot \bold{m}_k \right)

where ejk is a unit vector parallel to the line joining the centers of the two dipoles. rjk is the distance between two dipoles, mk and mj.

For two interacting nuclear spins:

 \bold{H} = - \frac{ \mu_0 }{ 4 \pi } \frac{ \gamma_j \gamma_k \hbar^2}{ r_{jk}^3 } \left( 3 (\bold{I}_j \cdot \bold{e}_{jk})  (\bold{I}_k \cdot \bold{e}_{jk}) - \bold{I}_j \cdot \bold{I}_k \right)

γj, γk and rjk are gyromagnetic ratios of two spins and spin-spin distance respectively.

Dipolar coupling and NMR spectroscopy

The direct dipole-dipole coupling is very useful for molecular structural studies, since it depends only on known physical constants and the inverse cube of internuclear distance. Estimation of this coupling provides a direct spectroscopic route to the distance between nuclei and hence the geometrical form of the molecule, or additionally also on intermolecular distances in the solid state leading to NMR crystallography notably in amorphous materials. Although internuclear magnetic dipole couplings contain a great deal of structural information, in isotropic solution, they average to zero as a result of rotational diffusion. However, their effect on nuclear spin relaxation results in measurable nuclear Overhauser effects (NOEs).

The residual dipolar coupling (RDC) occur if the molecules in solution exhibit a partial alignment leading to an incomplete averaging of spatially anisotropic magnetic interactions i.e. dipolar couplings. RDC measurement provides information on the global folding of the protein-long distance structural information. It also provides information about "slow" dynamics in molecules


  • Malcolm H. Levitt , Spin Dynamics: Basics of Nuclear Magnetic Resonance. ISBN 0-471-48922-0.

See also

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Magnetic dipole-dipole interaction — Magnetic dipole dipole interaction, also called dipolar coupling, refers to the direct interaction between two magnetic dipoles. The energy of the interaction is as follows:: old{H} = frac{ mu 0 } {4 pi r {jk}^3 } left( 3 (old{m} j cdot old{e} …   Wikipedia

  • Magnetic dipole transition — The interaction of an electromagnetic wave with an electron bound in an atom or molecule can be described by time dependent perturbation theory. Magnetic dipole transitions describe the dominant effect of the coupling to the magnetic part of the… …   Wikipedia

  • Magnetic dipole — A magnetic dipole is the limit of either a closed loop of electric current or a pair of poles as the dimensions of the source are reduced to zero while keeping the magnetic moment constant. It is a magnetic analogue of the electric dipole, but… …   Wikipedia

  • Electron magnetic dipole moment — In atomic physics, the magnetic dipole moment of an electron is caused by its intrinsic property of spin within a magnetic field. Explanation of magnetic momentThe electron is a negatively charged particle with angular momentum. A rotating… …   Wikipedia

  • Magnetic moment — Electromagnetism Electricity · …   Wikipedia

  • Magnetic field — This article is about a scientific description of the magnetic influence of an electric current or magnetic material. For the physics of magnetic materials, see magnetism. For information about objects that create magnetic fields, see magnet. For …   Wikipedia

  • Dipole — This article is about the electromagnetic phenomenon. For other uses, see dipole (disambiguation). The Earth s magnetic field, approximated as a magnetic dipole. However, the N and S (north and south) poles are labeled here geographically, which… …   Wikipedia

  • Interaction magnétique dipôle-dipôle — L’interaction magnétique dipôle dipôle, aussi appelée couplage dipolaire, fait référence à l interaction directe entre deux dipôles magnétiques. L énergie de cette interaction s exprime de la manière suivante : où ejk est un vecteur unité… …   Wikipédia en Français

  • Magnetic force microscope — MFM images of 3.2 GB and 30 GB computer hard drive surfaces. Magnetic force microscope (MFM) is a variety of atomic force microscope, where a sharp magnetized tip scans a magnetic sample; the tip sample magnetic interactions are detected and used …   Wikipedia

  • Magnetic monopole — It is impossible to make magnetic monopoles from a bar magnet. If a bar magnet is cut in half, it is not the case that one half has the north pole and the other half has the south pole. Inst …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”