Catapult mechanism for fast particle emission in fission and heavy ion reactions

Abstract

The fission process of slabs of nuclear matter is modelled in TDHF approximation by adding an initial collective velocity field to the static self-consistent solution. In dependence on its amplitude either large amplitude density oscillations are excited or fission occurs. The final disintegration of the slab proceeds on a time scale of 10−22s and is characterized by a sharp peak in the actual velocity field in the region of the “snatching” inner low density tails. A characteristic time later corresponding to the transit time of a nucleon across the fragment with mean velocity being the Fermi velocity plus twice the maximum “snatching” velocity, a low density lump correlated with a peak in the velocity field emerges in front of the fragments. We call these particles “catapult particles”. Recent experimental results possibly provide evidence for catapult neutrons in low-energy fission. We also speculate on the significance of the catapult mechanism for fast particle emission in the exit channel of heavy ion reactions.