Asymmetry effects on nuclear fragmentation

We show the possibility of extracting important information on the symmetry term of the Equation of State (EOS) directly from multifragmentation react ions using stable isotopes with different charge asymmetries. We study n-ri ch and n-poor Sn + Sn collisions at 50AMeV using a new stochastic transport approach with all isospin effects suitably accounted for. For central coll isions a chemical component in the spinodal instabilities is clearly seen. This effect is reduced in the neck fragmentation observed for semiperiphera l collisions, pointing to a different nature of the instability. In spite o f the low asymmetry tested with stable isotopes the results are showing an interesting and promising dependence on the stiffness of the symmetry term, with an indication towards an increase of the repulsion above normal densi ty.