Isoscaling in central 124Sn+64Ni, 112Sn+58Ni collisions at 35 A MeV

Sn-124 + Ni-64 and Sn-112 + Ni-58 reactions at 35 A MeV incident energy were studied by using the 688 Si-CsI telescopes of the forward part (1degrees less than or equal to theta(lab) less than or equal to 30degrees) of CHIMERA multi-detector. The most central part, 1% of the total measured cross section was selected by means of a multidimensional analysis of the experimental observables. The detected isotopes of light fragments (3 less than or equal to Z less than or equal to 8) provided information on breakup temperatures of the emitting sources. The space-time structure of these sources was deduced from fragment correlations. An odd-even effect in the fragment production, enhanced by the isospin of the entrance channel, was observed. Freeze-out unbound neutron-to-proton relative densities for both studied reactions have been deduced, indicating for a possible isospin distillation mechanism related to a phenomenon of the liquid-gas phase transition in asymmetric systems. (C) 2003 Elsevier B.V. All rights reserved.