R-Process Freezeout, Nuclear Deformation, and the Rare-Earth Element Peak

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.