RESUMO
Isotopic effects in the fragmentation of excited target residues following collisions of 12C on (112,124)Sn at incident energies of 300 and 600 MeV per nucleon were studied with the INDRA 4pi detector. The measured yield ratios for light particles and fragments with atomic number Z < or = 5 obey the exponential law of isotopic scaling. The deduced scaling parameters decrease strongly with increasing centrality to values smaller than 50% of those obtained for the peripheral event groups. Symmetry-term coefficients, deduced from these data within the statistical description of isotopic scaling, are near gamma = 25 MeV for peripheral and gamma < 15 MeV for central collisions.
RESUMO
Multifragmentation of a "fused system" was observed for central collisions between 32 MeV/nucleon 129Xe and (nat)Sn. Most of the resulting charged products were well identified due to the high performances of the INDRA 4pi array. Experimental higher-order charge correlations for fragments show a weak but nonambiguous enhancement of events with nearly equal-sized fragments. Supported by dynamical calculations in which spinodal decomposition is simulated, this observed enhancement is interpreted as a "fossil" signal of spinodal instabilities in finite nuclear systems.
RESUMO
Spallation residues produced in 1 GeV per nucleon 208Pb on proton reactions have been studied using the Fragment Separator facility at GSI. Isotopic production cross sections of elements from 61Pm to 82Pb have been measured down to 0.1 mb with a high accuracy. The recoil kinetic energies of the produced fragments were also determined. The obtained cross sections agree with most of the few existing gamma-spectroscopic data. The data are compared with different intranuclear-cascade and evaporation-fission models. Drastic deviations were found for a standard code used in technical applications.
