  We undertake herein to derive the Wigner-Wilkins [W-W] neutron/nucleus
scattering kernel, a foundation stone in neutron thermalization theory, on the
basis of a self-contained calculation in quantum mechanics. Indeed, a
quantum-mechanical derivation of the W-W kernel is available in the literature,
cited below, but it is, in our opinion, robbed of conviction by being couched
in terms of an excessive generality. Here, by contrast, we proceed along a
self-contained route relying on the Fermi pseudopotential and a first-order
term in a time-dependent Born approximation series. Our calculations are fully
explicit at every step and, in particular, we tackle in its every detail a
final integration whose result is merely stated in the available literature.
Furthermore, and perhaps the most important point of all, we demonstrate that
the quantum-mechanical W-W kernel outcome is identical down to the last iota
with its classical antecedent, classical not only by virtue of historical
precedence but also by being based on classical Newtonian mechanics.
