INDRA collaboration

PRL 94, 162701 (2005)

Preprint on arXiv

Isotopic effects in the fragmentation of excited target residues following collisions of 12C on 112,124Sn at incident energies of 300 and 600 MeV per nucleon were studied with the INDRA 4π detector. The measured yield ratios for light particles and fragments with atomic number Z≤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 γ=25 MeV for peripheral and γ<15 MeV for central collisions.