This is an animated GIF image, generated from a purely classical Molecular Dynamics simulation. The form of the potential is:

V(r) = a/r^8 - b/r^4 + c/r

The constants a, b and c were chosen to reproduce the binding energy, saturation density and spontaneous fission size for nuclei.

At this beam energy, the nuclear matter heats up and expands to near the point where it would become an irreversible explosion. As it collapses back into a ball, the coulomb force allows the initially rotationally invariant geometry to form an off-axis tube. This hot tube then undergoes a fission-like decay.

This code, which can generate a movie from any simulation which writes down phase space points at various times can be copied from Scott Pratt's home page.