Effect of system N/Z on the enhanced production of even-Z fragments observed in heavy ion reactions - art. no. 014601

The enhancement in the production of even-Z nuclei observed in nuclear fiss ion has also been observed in fragments produced from heavy ion collsions. Beams of Ar-40, Cl-40, and Ca-40 at 25 MeV/nucleon were impinged on Fe-58 a nd Ni-58 targets. The resulting fragments were detected using the MSU 4 pi detector array, which had additional silicon detectors for better isotopic resolution. Comparison of the ratios of yields for each element showed enha ncement of even-Z fragment production. The enhancement was more pronounced for reactions with a greater difference in the N/Z of the compound system. However, this effect was less for systems that were more neutron rich. The average N/Z for fragments also displayed an odd-even effect with a lower av erage N/Z for the even-Z fragments. This is related to the greater availabi lity of neutron-poor isotopes for even-Z nuclei.