1,144 research outputs found
The equation of state and symmetry energy of low density nuclear matter
The symmetry energy of nuclear matter is a fundamental ingredient in the
investigation of exotic nuclei, heavy-ion collisions and astrophysical
phenomena. A recently developed quantum statistical (QS) approach that takes
the formation of clusters into account predicts low density symmetry energies
far above the usually quoted mean field limits. A consistent description of the
symmetry energy has been developed that joins the correct low-density limit
with values calculated from quasi-particle approaches valid near the saturation
density. The results are confronted with experimental values for free symmetry
energies and internal symmetry energies, determined at sub-saturation densities
and temperatures below 10 MeV using data from heavy-ion collisions. There is
very good agreement between the experimental symmetry energy values and those
calculated in the QS approachComment: 16 pages, 10 figures. arXiv admin note: text overlap with
arXiv:0908.234
Nucleation and cluster formation in low-density nucleonic matter: A mechanism for ternary fission
Ternary fission yields in the reaction 241Pu(nth,f) are calculated using a
new model which assumes a nucleation-time moderated chemical equilibrium in the
low density matter which constitutes the neck region of the scissioning system.
The temperature, density, proton fraction and fission time required to fit the
experimental data are derived and discussed. A reasonably good fit to the
experimental data is obtained. This model provides a natural explanation for
the observed yields of heavier isotopes relative to those of the lighter
isotopes, the observation of low proton yields relative to 2H and 3H yields and
the non-observation of 3He, all features which are shared by similar thermal
neutron induced and spontaneous fissioning systems.Comment: 6 pages, 3 figure
Isocaling and the Symmetry Energy in the Multifragmentation Regime of Heavy Ion Collisions
The ratio of the symmetry energy coefficient to temperature, , in
Fermi energy heavy ion collisions, has been experimentally extracted as a
function of the fragment atomic number using isoscaling parameters and the
variance of the isotope distributions. The extracted values have been compared
to the results of calculations made with an Antisymmetrized Molecular Dynamics
(AMD) model employing a statistical decay code to account for deexcitation of
excited primary fragments. The experimental values are in good agreement with
the values calculated but are significantly different from those characterizing
the yields of the primary AMD fragments.Comment: 12 pages, 6 figure
Irreversible Magnetization Deep in the Vortex-Liquid State of a 2D Superconductor at High Magnetic Fields
The remarkable phenomenon of weak magnetization hysteresis loops, observed
recently deep in the vortex-liquid state of a nearly two-dimensional (2D)
superconductor at low temperatures, is shown to reflect the existence of an
unusual vortex-liquid state, consisting of collectively pinned crystallites of
easily sliding vortex chains.Comment: 5 pages, 4 figure
Constraint Molecular Dynamics approach to Fermionic systems
We propose a Constraint Molecular Dynamics model for Fermionic system. In
this approach the equations of motion of wave packets for the nuclear many-body
problem are solved by imposing that the one-body occupation probability
can assume only values less or equal to 1. This condition
reflects the Fermionic nature of the studied systems and it is implemented with
a fast algorithm which allows also the study of the heaviest colliding system.
The parameters of the model have been chosen to reproduce the average binding
energy and radii of nuclei in the mass region . Some comparison
to data is given.Comment: 11 pages and 6 figure
Symmetry energy of dilute warm nuclear matter
The symmetry energy of nuclear matter is a fundamental ingredient in the
investigation of exotic nuclei, heavy-ion collisions and astrophysical
phenomena. New data from heavy-ion collisions can be used to extract the free
symmetry energy and the internal symmetry energy at subsaturation densities and
temperatures below 10 MeV. Conventional theoretical calculations of the
symmetry energy based on mean-field approaches fail to give the correct
low-temperature, low-density limit that is governed by correlations, in
particular by the appearance of bound states. A recently developed quantum
statistical (QS) approach that takes the formation of clusters into account
predicts symmetry energies that are in very good agreement with the
experimental data. A consistent description of the symmetry energy is given
that joins the correct low-density limit with quasiparticle approaches valid
near the saturation density.Comment: 4 pages, 2 figures, 1 tabl
An experimental survey of the production of alpha decaying heavy elements in the reactions of U +Th at 7.5-6.1 MeV/nucleon
The production of alpha particle decaying heavy nuclei in reactions of
7.5-6.1 MeV/nucleon U +Th has been explored using an in-beam
detection array composed of YAP scintillators and gas ionization chamber-Si
telescopes. Comparisons of alpha energies and half-lives for the observed
products with those of the previously known isotopes and with theoretically
predicted values indicate the observation of a number of previously unreported
alpha emitters. Alpha particle decay energies reaching as high as 12 MeV are
observed. Many of these are expected to be from decay of previously unseen
relatively neutron rich products. While the contributions of isomeric states
require further exploration and specific isotope identifications need to be
made, the production of heavy isotopes with quite high atomic numbers is
suggested by the data.Comment: 12 pages, 12 figure
- …