Correlation between fragment lifetime, alignment, and composition in heavy ion collision simulations

When two nuclei collide at intermediate collision energies there is a tendency for a neck to form between the projectile and the target, and for this neck to be neutron-rich compared to the whole system. Following the neck rupture, the resulting excited projectile-like fragment (PLF*) and the target-like fragment are typically deformed and are likely to undergo dynamical decay. Because of the neutron-rich neck, the PLF* typically begins with a more neutron-rich side and a less neutron-rich side. The PLF* may further break into two more fragments (one more neutron-rich and one less neutron-rich). Of interest is the relationship between how long the PLF* lasts before breaking, the angular alignment of the two fragments it breaks into, and how much the neutron and proton density evens out across the PLF* while it exists. The time scales at which this process happens are on the order of zeptoseconds. While the timescale at which PLF* lasts cannot be measured directly in an experiment, the whole process can be simulated with molecular dynamics model calculations. Data from an Antisymmetrized Molecular Dynamics (AMD) simulation of a zinc-70 on zinc-70 collision with energy of 35MeV/nucleon was analyzed to determine the relationship between the lifetime of the PLF*, the angular alignment of the two largest fragments resulting from the PLF*, and the proton/neutron richness of the two fragments.