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THE QUANTUM [xvi. 3
have not as yet been fully investigated, but it must be remembered
that these were implicit in the magneton of A. L. Parson and
were taken for granted in the static models of Lewis and Lang
muir. It need only be said here that the difficulties of explaining
the diamagnetic properties of hydrogen and helium when the
Bohr model is employed, disappear on the introduction of electrons
which possess magnetic moment.
The remarkable results obtained by employing the spinning
electron in Bohr's atomic model suggest the idea that the proton
also may be capable of a quantized spin. If, as is generally
assumed, the proton is the positive electron, it seems natural
to assume that if the negative electron can spin with unit angular
momentum the positive may do the same. Again, it may be
easier to understand the structure of a complex nucleus if the
units of which it is composed can act as elementary magnets.
Duane * has attempted to explain corpuscular emission from a
radioactive nucleus on these lines. According to O. W. Richard
son, f it is probable that the electron loses its angular momentum
when it enters into the nucleus, but the magnitude of the
mechanical gyromagnetic anomaly makes it necessary to admit
the existence of a quantized spin of the nucleus as a whole.
Finally experiments on the deflection of protons and alpha
particles in collision with an atomic nucleus lend support to the
idea that a magnetic field exists in the vicinity of a nucleus.
3. The Gyromagnetic Electron of L. V. King
A rotating spherical charge sets up a magnetic field, which
was investigated by Maxwell in 1870. The internal field is uniform
and of strength §eoo/a, while the external field is that of a mag
netic doublet of moment |ecoa 2 , where co is the angular velocity
and a the radius of the sphere.
A simple type of spinning electron based on Maxwell’s work
has been discussed by L. V. King,! who has attempted to give
a theory of atomic structure and radiation by using classical
electrodynamics. His work is of great interest, and although it
obviously cannot claim finality, the attempt shows that the
resources of classical theory have by no means been exhausted.
When the spinning electron is moving in a specified direction
with velocity v, it is deformed by translation into an ellipsoid,
the short axis being in the direction of motion. Regarding this
as a real, physical deformation, the total energy of the field due
both to translation and to spin, including the work done by the
boundary stresses (probably magnetic in origin) is similar in form
* Duane, Phys. Rev., vol. 5, p. 335, 1915.
t Richardson, Nature, vol. 117, p. 652, 1926.
t L. V. King, Gyromagnetic Electrons (Louis Carrier, Montreal, 1926).