  We use network calculations of r-process nucleosynthesis to explore the
origin of the peak in the solar r-process abundance distribution near nuclear
mass number A = 160. The peak is due to a subtle interplay of nuclear
deformation and beta decay, and forms not in the steady phase of the r-process,
but only just prior to freezeout, as the free neutrons rapidly disappear. Its
existence should therefore help constrain the conditions under which the
r-process occurs and freezes out.
