MULTIFRAGMENTATION, LINK BETWEEN FISSION AND THE LIQUID-GAS PHASE-TRANSITION

Nuclear multifragmentation is viewed as the natural extension of nuclear fission towards higher excitations. The role of the fissility to trigger sequential fragmentation and later simultaneous multifragmentation is shown in a simple analytical example. At even higher excitation nuclear multifragmentation continues into the liquid to gas transition of a finite piece of nuclear matter. With the help of microcanonical Metropolis-Monte Carlo we study multifragmentation as a realistic example of thermodynamics of a finite many-body system subjected to long-range forces using the most basic principles of statistical physics. This allows for a consistent calculation of the entropy including its non trivial partitional part. In the case of nuclear fragmentation it is essentially different from the expression used in the literature. We find a proper phase-transition with a rapid rise of the entropy linked to the onset of statistical fragmentation into several large fragments: A situation quite singular in nuclear physics but generic for many other fields in physics e.g. astrophysics and atomic clusters.