Electronic nucleon-to-nucleon coupling.
"J-coupling (also called indirect dipole dipole coupling) is the coupling between two nuclear spins due to the influence of bonding electrons on the magnetic field running between the two nuclei. J-coupling contains information about dihedral angles, which can be estimated using the Karplus equation. It is an important observable effect in 1D nuclear magnetic resonance spectroscopy." More: Wikipedia.org
- Earth's Field NMR http://en.wikipedia.org/wiki/Earth%27s_field_NMR
- Residual Dipolar Coupling http://en.wikipedia.org/wiki/Residual_dipolar_coupling
- Proton NMR http://en.wikipedia.org/wiki/Proton_NMR
- Magnetic dipole–dipole interaction http://en.wikipedia.org/wiki/Magnetic_dipole-dipole_interaction