Electronic Current-density Induced By Nuclear Magnetic Dipoles

Magnetic point-group symmetries of high order in molecules can be described via the electronic current density vector field induced by a set of ideal magnetic dipoles properly placed in space. The expression for the diamagnetic Larmor-type current density induced in the electrons of a molecule by intrinsic nuclear magnetic dipole moments can be obtained via classical electrodynamics, but quantum mechanics is necessary to account for other terms: the Ramsey relations for paramagnetic spin-orbit, spin-dipolar, Fermi contact, and cross Fermi contact/spin-dipolar contributions to (indirect) spin-spin nuclear magnetic coupling can be rewritten in terms of second-rank current density tensors. Maps of current densities induced by two nuclear dipoles could be used to visualize the electron coupled interaction between two nuclei and to rationalize the coupling mechanism