Final Activity Report Summary - MULTIFRAGMENTATION (Nuclear thermo-dynamics) A method for identifying statistical equilibrium stages in the dynamics of nuclear multi-fragmentation in heavy ion collisions at intermediate energies was successfully developed. The approach has been tested for multi-fragmentation reactions induced by 129 Xe projectiles on 119 Sn targets at beam laboratory energies of 32 and 50 AMeV. The method evaluated the equilibrium expectations using the microcanonical multi-fragmentation model (MMM) and the reaction dynamics was simulated by means of the stochastic mean field (SMF) transport theory. A unique solution, corresponding to the maximum population of the system phase space, could be identified at both energies. The related phase-space configuration of the system dynamical evolution was at the level of a pre-fragment structure, i.e. of clusters in a compact form, not fully separated and still with nuclear interactions, which was not a freeze-out configuration. In the higher energy events the stage with an occupied huge part of the available phase space was still present if a considerable amount of radial collective flow was accounted for. Equilibration times and volumes could be well identified. The conclusions were that nuclear multi-fragmentation processes could be described in a statistical microcanonical frame only after a very careful choice of the fragmenting equilibrated source and with the inclusion of external collective constraints. In spite of the earlier termination of the project, due to the fellow personal reasons, the results largely achieved the research objectives of the original proposal.
