The origins, history, and present status of the controversy surrounding a quantum description of the NMR signal as being due to radio waves are traced. With the Principle of Relativity and Coulomb's Law as formal starting points and the minimum of mathematics needed for understanding, the derivation of a classical electromagnetic theory of signal reception is first given. The agreement between that classical theory and a recent NMR experiment is then presented, leading to proof that, except for the highest field imaging experiments, there is no significant contribution of radio waves to the sig- nal. Attention is drawn to the very different properties of the near and far energy, momenta, and fields inherent in the derivation. The role of the Correspondence Principle in formulating a quantum description is then emphasized and it is shown that the stand- ard NMR interpretation of Dicke's theory of coherent spontaneous emission—that the latter is responsible for the NMR signal—cannot be correct. Finally, the author speculates on some of the intriguing relationships found in the classical electrodynamics of NMR signal reception and attempts to relate them to a common quantum electrodynamic precept of near field interaction: that the free induction decay voltage present at the terminals of an open-circuit receiving coil is based on an exchange of virtual photons between the nuclei in a sample and the free electrons in a receiving coil. 2009 Crown in the right of Canada. Concepts Magn Reson Part A 34A: 193-216, 2009.

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Comment on “An elementary account of the factor of 4/3 in the electromagnetic mass,” by Patrick Moylan [Am. J. Phys. 63 (9), 818–820 (1995)]

The origins and present status of the radio wave controversy in NMR

The point charge and the extended charge as models of the classical electron are studied. The problems inherent to each model with respect to self-interaction are disclosed and the possible solutions are analysed. The possible relation between these models is also discussed. We argue that a totally electromagnetic electron, as well as a point electron, is beyond the scope of classical electrodynamics. This work is intended as a complement to F. Rohrlich's recent account in the sense that it points at challenges still present in the way to a deeper understanding of the electron.

Models of the classical electron after a century

The electric field of an orbiting charge or electron observed in the rotating frame takes on a circular trajectory with a maximum radius of $$R=\frac{c}{\omega '}$$
 . The resultant extended electromagnetic structure is used to derive the spin–orbit energy of the orbiting electron. A surprising result of the derived expression is that the orbital velocity has a specific value (
 $$\beta _0 = \frac{1}{136.96}$$
 ) in close agreement (
 $$99.94\%$$
 ) with the experimentally determined value for the fine structure constant (
 $$\hbar =\frac{ke^2}{c}\frac{1}{\alpha _{\mathrm{exp}}} =\frac{ke^2}{c}\frac{1}{\beta _0} \rightarrow \alpha _{\mathrm{exp}}=\beta _0$$
 ). Furthermore, the derived spin–orbit expression does not include a g-factor (i.e $$g=1$$
 ) which means that the Larmor and Thomas precessions are equal and opposite, resulting in zero net precession in the lab frame. These results suggest that the quantised fine structure constant and by extension Planck’s constant, are a natural extension of classical electromagnetism and conservation of energy in a rotating frame.

Comment on “An elementary account of the factor of 4/3 in the electromagnetic mass,” by Patrick Moylan [Am. J. Phys. 63 (9), 818–820 (1995)]

Citations

The origins and present status of the radio wave controversy in NMR

Models of the classical electron after a century

Electromagnetic Angular Momentum of an Orbiting Charge

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