Rutherford Atom Revisited

Niels Bohr won the Nobel Prize in 1922 largely on the merits of his
quantized hydrogen atom model, which was based on an analogy to the
Solar System. Extension of the model to heavier (more complicated)
atoms fared less well, however, and stellar/atomic analogies began to
fall from grace.

Subsequently, quantum mechanics evolved rapidly and successfully,
and in a way that made the concept of stellar/atomic comparisons seem
like a misguided idea whose original success was more fluke than
physics. What was once regarded as a brilliant unifying idea became
synonymous with "naivete", "hard-headedness" or "mental impairment".

Most people think that the story of this concept stops there. In
fact, the empirical case for self-similarity ("parts" and "wholes"
have similar morphologies, kinematics and/or dynamics) between atomic
and stellar systems has become surprisingly strong again.

Low energy state atoms clearly were not the correct choice for
Solar System analogues, but atoms in very high n (principal quantum
number) states are a different matter. As early as 1980 Metcalf could
justifiably state in Nature (vol. 284, pp. 127-131):
"Many properties of Rydberg atoms can be understood correctly
in terms of relatively simple notions (Bohr model) used to
describe hydrogen atoms... The picture that emerges of a
Rydberg atom is one of an ion core and an isolated electron
very far away, floating lazily around in a slow orbit, much
like a distant planet of the Solar System."

Since that time there has been a growing body of evidence
(published in Phys. Rev. Lett., Phys. Rev. A, Phys. Lett, etc.) that
supports the rehabilitation of physically meaningful stellar/atomic
analogies. Authors had good reason to refer to high n Rydberg atoms
as "planetary atoms". One by one the morphological and kinematic
distinctions between high n atoms and Solar-type systems began to
dissolve. One of the most resilient distinctions between planetary
models on the two different scales (factor of ~10^18 in size) has been
that highly localized, particle-like electron wavepackets would
undergo fairly rapid spreading. Now it appears that this barrier to
stellar/atomic self-similarity may also have fallen.

In their recent paper entitled "Rutherford atom in quantum theory"
(Phys. Rev. A, vol. 67, 032503, 2003), Kalinski et al. make the
following statements.

"We predict the existence of a self-sustained one-electron
wave packet moving on a circular orbit in the helium atom.
The wave packet is localized in space, but does not spread
in time. This is a realization WITHIN QUANTUM THEORY of a
classical object that has been called a "Rutherford atom,"
a localized planetary electron on an unquantized circular
orbit under the influence of a massive charged core."

So, can we now say that the study of stellar/atomic self-similarity
involving direct analogies between physical properties of atoms and
stellar scale systems is legitimate science with potentially profound
implications? Or is the concept still anathema?


[[Mod. note -- The Kalinski et al paper can be found at
http://www.optics.rochester.edu:8080...alinski031.pdf
-- jt]]