Properties of the initial participant matter interaction zone in near-Fermi-energy heavy-ion collisions

The sizes, temperatures, and free neutron-to-proton ratios of the initial interaction zones produced in the collisions of 40 MeV/nucleon Ar-40+Sn-112 and 55 MeV/nucleon Al-27+Sn-124 are derived using total detected neutron plus charged particle multiplicity as a measure of the impact parameter range and number of participant nucleons. The size of the initial interaction zone, determined from a coalescence model analysis, increases significantly with decreasing impact parameter. The temperatures and free neutron-to-proton ratios in the interaction zones are relatively similar for different impact parameter ranges and evolve in a similar fashion.