  The Mott problem asks: Is there a microscopic physical mechanism - based
(explicitly or implicitly) only on Schroedinger's equation - that explains why
a single alpha particle emitted in a single spherically symmetric s-wave
nuclear decay produces a manifestly non-spherically-symmetric single track in a
cloud chamber? This is a variant of the more general quantum measurement
problem. Earlier, we proposed such a mechanism, drawing on quantum-mechanical
Coulomb scattering and the thermal behavior of supersaturated vapors. Our
analysis implied that, in a large enough sample, the probability that a track
originates at distance R from the decay source is proportional to 1/R^2, with a
proportionality constant which we expressed in terms of more fundamental
parameters involving diverse physical processes, but were unable to estimate at
the time. More recently, we tested the 1/R^2 law opportunistically using
pedagogical cloud chamber video posted on the Internet. In the present paper,
we draw on the chemical physics literature for an independent estimate of the
proportionality constant. The estimate is rough, but within about 1.7 orders of
magnitude (factor of 50) of a rough value that we derive directly from the
video data. Given the crudeness of the experimental data, the roughness of the
numerical estimates, and the extreme spread of concentrations involved (air
molecules vs. subcritical vapor clusters of specific sizes), we view this level
of agreement as significant, at this stage in the theory's development.
