Isoscaling of heavy projectile residues andequilibration in peripheral heavy-ion collisions below the Fermi energy
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2014 American Physical Society. The isoscaling of heavy projectile residues from peripheral heavy-ion reactions at 15-25 MeV/nucleon is employed to obtain information on the process of N/Z equilibration. Recent mass spectrometric data of projectile residues from the reactions of Kr86 (15 MeV/nucleon) with Ni64,58 and Sn124,112 were first analyzed. The isotopically resolved yield distributions of the fragments in the range Z=26-39 were employed for the isoscaling analysis. The yield ratios R21(N,Z) of the fragments from each pair of systems exhibit isoscaling (i.e., an exponential dependence on the fragment neutron number N for each atomic number Z) with the isoscaling parameter increasing with decreasing (or increasing) Z away from the projectile. This variation is related to the evolution toward N/Z equilibration with increasing energy dissipation estimated from the residue velocities. In parallel to the new heavy-residue isoscaling data of Kr86 at 15 MeV/nucleon, our previous data at 25 MeV/nucleon for the reactions Kr86+Sn124,112 and Ni64+Ni64,58, Ni64+Sn124,112, as well as our data at 15 MeV/nucleon of the lighter system Ar40+Ni64,58, were analyzed in a similar way. Calculations with the stochastic nucleon-exchange model DIT (deep inelastic transfer) and the microscopic many-body model CoMD (constrained molecular dynamics) provided an overall fair description of data and valuable guidance for their interpretation. Interestingly, the data of the Kr86+Ni,Sn reactions at 15 MeV/nucleon show a retardation of the process of N/Z equilibration which, as suggested by the CoMD calculations, is indicative of the collective character of the process. This retardation is not present in the investigated systems at 25 MeV/nucleon (and the light Ar40+Ni systems at 15 MeV/nucleon), whose behavior is found to be consistent with stochastic nucleon exchange.
author list (cited authors)
Souliotis, G. A., Fountas, P. N., Veselsky, M., Galanopoulos, S., Kohley, Z., McIntosh, A., Yennello, S. J., & Bonasera, A.
complete list of authors
Souliotis, GA||Fountas, PN||Veselsky, M||Galanopoulos, S||Kohley, Z||McIntosh, A||Yennello, SJ||Bonasera, A