Abstract
Nuclear thermodynamics studies evidenced the existence of a liquid-gas type phase transition, that manifests through multifragmentation and may originate from spinodal instabilities. Several signals typical of finite systems were experimentally observed. The spinodal region of the phase diagram is theoretically predicted to shrink for systems away from the valley of stability. What happens to the signals of phase transition for such systems should thus bring further information on the symmetry energy term of the nuclear equation of state.
Highlights
During the last decades nuclear thermodynamics was widely studied through heavy-ion collisions during which a nucleus can be heated, compressed, diluted These systems are expected to undergo a liquidgas type phase transition, due to the analogy between the nuclear interaction and the force acting on Van der Waals fluids, that manifests through nuclear multifragmentation
Isospin effects on nuclear thermodynamics at subnormal densities and incident energies lower than 100 A MeV are theoretically predicted; they should be more visible for neutron-rich nuclei as Coulomb effects impede those of the symmetry potential
The hot nucleus asymmetry is uncertain in experiments, due to preequilibrium emission and evaporation, which lead for instance to contradictory observations concerning isospin effects on caloric curves
Summary
During the last decades nuclear thermodynamics was widely studied through heavy-ion collisions during which a nucleus (or a nuclear system) can be heated, compressed, diluted These systems are expected to undergo a liquidgas type phase transition, due to the analogy between the nuclear interaction and the force acting on Van der Waals fluids, that manifests through nuclear multifragmentation Finite systems such as nuclei show specific behaviours in the transition region. Most of the predicted specific signals were experimentally evidenced, they indicate that multifragmentation may be induced by spinodal instabilities [1, 2] This happens when the system evolves through the mechanically unstable spinodal region of the phase diagram, located at densities ρ ≤ ρ0 and temperature below the critical temperature. After a brief review of the nuclear phase transition signals we shall discuss some experimental results showing the influence of isospin on the caloric curve, on isospin distillation and on the level density parameter
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