4,778 research outputs found
Mass distributions for nuclear disintegration from fission to evaporation
By a proper choice of the excitation energy per nucleon we analyze the mass
distributions of the nuclear fragmentation at various excitation energies.
Starting from low energies (between 0.1 and 1 MeV/nucleon) up to higher
energies about 12 MeV/n, we classified the mass yield characteristics for heavy
nuclei (A>200) on the basis of Statistical Multifragmentation Model. The
evaluation of fragment distribution with the excitation energy show that the
present results exhibit the same trend as the experimental ones.Comment: 5 pages, 3 figure
Isospin and symmetry energy effects on nuclear fragment production in liquid-gas type phase transition region
We have demonstrated that the isospin of nuclei influences the fragment
production during the nuclear liquid-gas phase transition. Calculations for
Au197, Sn124, La124 and Kr78 at various excitation energies were carried out on
the basis of the statistical multifragmentation model (SMM). We analyzed the
behavior of the critical exponent tau with the excitation energy and its
dependence on the critical temperature. Relative yields of fragments were
classified with respect to the mass number of the fragments in the transition
region. In this way, we have demonstrated that nuclear multifragmentation
exhibits a 'bimodality' behavior. We have also shown that the symmetry energy
has a small influence on fragment mass distribution, however, its effect is
more pronounced in the isotope distributions of produced fragments.Comment: 8 pages, 9 figures, accepted for publication in EPJ
Modification of surface energy in nuclear multifragmentation
Within the statistical multifragmentation model we study modifications of the
surface and symmetry energy of primary fragments in the freeze-out volume. The
ALADIN experimental data on multifragmentation obtained in reactions induced by
high-energy projectiles with different neutron richness are analyzed. We have
extracted the isospin dependence of the surface energy coefficient at different
degrees of fragmentation. We conclude that the surface energy of hot fragments
produced in multifragmentation reactions differs from the values extracted for
isolated nuclei at low excitation. At high fragment multiplicity, it becomes
nearly independent of the neutron content of the fragments.Comment: 11 pages with 13 figure
The role of bulk energy in nuclear multifragmentation
Because of thermal expansion and residual interactions, hot nuclear fragments
produced in multifragmentation reactions may have lower nucleon density than
the equilibrium density of cold nuclei. In terms of liquid-drop model this
effect can be taken into account by reducing the bulk energy of fragments. We
study the influence of this change on fragment yields and isotope distributions
within the framework of the statistical multifragmentation model. Similarities
and differences with previously discussed modifications of symmetry and surface
energies of nuclei are analyzed.Comment: 8 pages, 7 figures, to be published in Phys. Rev.
Theoretical analyses of FAZIA data with a statistical approach
We have performed systematical calculations on multifragmentation picture for peripheral 84Kr+112,124Sn collisions at an incident beam energy of 35MeV/nucleon. In order to investigate the Coulomb and angular momentum effects for these reactions, the calculations are performed to reproduce the data for charge distributions of the fragments, on the basis of the microcanonical Markov chain approach within the statistical multifragmentation model
Experimental Signals of Phase Transition
The connection between the thermodynamics of charged finite nuclear systems
and the asymptotically measured partitions is presented. Some open questions,
concerning in particular equilibrium partitions are discussed. We show a
detailed comparison of the decay patterns in Au+ C,Cu,Au central collisions and
in Au quasi-projectile events. Observation of abnormally large fluctuations in
carefully selected samples of data is reported as an indication of a first
order phase transition (negative heat capacity) in the nuclear equation of
state.Comment: 8 pages, 8th International Conference on Nucleus-Nucleus Collisions,
Moscow 200
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