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Magnetic dipole–dipole interaction, also called dipolar coupling, refers to the direct interaction between two magnetic dipoles. Roughly speaking, the magnetic field of a dipole goes as the inverse cube of the distance, and the force of its magnetic field on another dipole goes as the first derivative of the magnetic field. It follows that ...
Intuitively, we may picture this as when one magnetic atom scatters an electron wave, which then scatters off another magnetic atom many atoms away, thus coupling the two atoms' spins. [ 2 ] Tadao Kasuya from Nagoya University later proposed that a similar indirect exchange coupling could occur with localized inner d-electron spins instead of ...
It is related to the prototypical Ising model, where at each site of a lattice, a spin {} represents a microscopic magnetic dipole to which the magnetic moment is either up or down. Except the coupling between magnetic dipole moments, there is also a multipolar version of Heisenberg model called the multipolar exchange interaction .
The final term, often known as the Fermi contact term relates to the direct interaction of the nuclear dipole with the spin dipoles and is only non-zero for states with a finite electron spin density at the position of the nucleus (those with unpaired electrons in s-subshells). It has been argued that one may get a different expression when ...
Example 1 H NMR spectrum (1-dimensional) of ethanol plotted as signal intensity vs. chemical shift.There are three different types of H atoms in ethanol regarding NMR. The hydrogen (H) on the −OH group is not coupling with the other H atoms and appears as a singlet, but the CH 3 − and the −CH 2 − hydrogens are coupling with each other, resulting in a triplet and quartet respectively.
A key example of this phenomenon is the spin–orbit interaction leading to shifts in an electron's atomic energy levels, due to electromagnetic interaction between the electron's magnetic dipole, its orbital motion, and the electrostatic field of the positively charged nucleus.
Temperature drift and device mismatches are the major causes of offset errors, and circuits employing direct coupling often integrate offset nulling mechanisms. Some circuits (like power amplifiers) even use coupling capacitors—except that these are present only at the input (and/or output) of the whole system but not between the individual ...
Förster coupling is the resonant energy transfer between excitons within adjacent QD's (quantum dots). The first studies of Forster were performed in the context of the sensitized luminescence of solids. Here, an excited sensitizer atom can transfer its excitation to a neighbouring acceptor atom, via an intermediate virtual photon.