8 research outputs found
Liquid-gas phase transition and Coulomb instability of asymmetric nuclear systems
We use a chiral SU(3) quark mean field model to study the properties of
nuclear systems at finite temperature. The liquid-gas phase transition of
symmetric and asymmetric nuclear matter is discussed. For two formulations of
the model the critical temperature, , for symmetric nuclear matter is
found to be 15.8 MeV and 17.9 MeV. These values are consistent with those
derived from recent experiments. The limiting temperatures for finite nuclei
are in good agreement with the experimental points.Comment: 14 pages, 6 figure
Liquid-gas phase transition and Coulomb instability of asymmetric nuclear systems
We use a chiral SU(3) quark mean field model to study the properties of
nuclear systems at finite temperature. The liquid-gas phase transition of
symmetric and asymmetric nuclear matter is discussed. For two formulations of
the model the critical temperature, , for symmetric nuclear matter is
found to be 15.8 MeV and 17.9 MeV. These values are consistent with those
derived from recent experiments. The limiting temperatures for finite nuclei
are in good agreement with the experimental points.Comment: 14 pages, 6 figure
Caloric Curves and Nuclear Expansion
Nuclear caloric curves have been analyzed using an expanding Fermi gas
hypothesis to extract average nuclear densities. In this approach the observed
flattening of the caloric curves reflects progressively increasing expansion
with increasing excitation energy. This expansion results in a corresponding
decrease in the density and Fermi energy of the excited system. For nuclei of
medium to heavy mass apparent densities ~ 0.4 rho_0 are reached at the higher
excitation energies.Comment: 4 pages, 3 figure
Multifragmentation and the liquid-gas phase transition: an experimental overview
Two roads are presently being followed in order to establish the existence of
a liquid-gas phase transition in finite nuclear systems from nuclear reactions
at high energy. The clean experiment of observing the thermodynamic properties
of a finite number of nucleons in a container is presently only possible with
the computer. Performed with advanced nuclear transport models, it has revealed
the first-order character of the transition and allowed the extraction of the
pertinent thermodynamic parameters. The validity of the applied theory is being
confirmed by comparing its predictions for heavy-ion reactions with exclusive
experiments.
The second approach is experimentally more direct. Signals of the transition
are searched for by analysing reaction data within the framework of
thermodynamics of small systems. A variety of potential signals has been
investigated and found to be qualitatively consistent with the expectations for
the phase transition. Many of them are well reproduced with percolation models
which places the nuclear fragmentation into the more general context of
partitioning phenomena in finite systems.
A wealth of new data on this subject has been obtained in recent experiments,
some of them with a new generation of multi-detector devices aiming at higher
resolutions, isotopic identification of the fragments, and the coincident
detection of neutrons. Isotopic effects in multifragmentation were addressed
quite intensively, with particular attention being given to their relation to
the symmetry energy and its dependence on density.Comment: 10 pages, 7 figures, Contribution to Proceedings of INPC2004,
Goeteborg, Sweden, June 27 - July 2, 200
Caloric curves and critical behavior in nuclei
Data from a number of different experimental measurements have been used to
construct caloric curves for five different regions of nuclear mass. These
curves are qualitatively similar and exhibit plateaus at the higher excitation
energies. The limiting temperatures represented by the plateaus decrease with
increasing nuclear mass and are in very good agreement with results of recent
calculations employing either a chiral symmetry model or the Gogny interaction.
This agreement strongly favors a soft equation of state. Evidence is presented
that critical excitation energies and critical temperatures for nuclei can be
determined over a large mass range when the mass variations inherent in many
caloric curve measurements are taken into account.Comment: In response to referees comments we have improved the discussion of
the figures and added a new figure showing the relationship between the
effective level density and the excitation energy. The discussion has been
reordered and comments are made on recent data which support the hypothesis
of a mass dependence of caloric curve