Evidence for Spinodal Decomposition in Nuclear Multifragmentation

Abstract : Multifragmentation of a ``fused system\'\' was observed for central collisions between 32 MeV/nucleon 129Xe and natSn. Most of the resulting charged products were well identified thanks to the high performances of the INDRA 4pi array. Experimental higher-order charge correlations for fragments show a weak but non ambiguous 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.