332 research outputs found
Limiting Temperatures and the Equation of State of Nuclear Matter
From experimental observations of limiting temperatures in heavy ion
collisions we derive Tc, the critical temperature of infinite nuclear matter.
The critical temperature is 16.6 +- 0.86 MeV. Theoretical model correlations
between Tc, the compressibility modulus, K the effective mass, and the
saturation density, rho_s, are exploited to derive the quantity
(K/m^*)**1/2*rho_s^{-1/3}$. This quantity together with calculations employing
Skyrme and Gogny interactions indicates a nuclear matter incompressibility in
moderately excited nuclei that is in excellent agreement with the value
determined from Giant Monopole Resonance data. This technique of extraction of
K may prove particularly useful in investigations of very neutron rich systems
using radioactive beams.Comment: 4 pages, 5 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
Towards the critical behavior for the light nuclei by NIMROD detector
The critical behavior for the light nuclei with A has been
investigated experimentally by the NIMROD multi-detectors. The wide variety of
observables indicate the critical point has been reached in the disassembly of
hot nuclei at an excitation energy of 5.60.5 MeV/u.Comment: 4 pages, 2 figures; Proceeding of 18th Nuclear Physics Division
Conference of the Euro. Phys. Society (NPDC18) "Phase transitions in strongly
interacting matter", Prague, 23.8.-29.8. 2004. To be published in Nuclear
Physics
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
Primary Isotope Yields and Characteristic Properties of the Fragmenting Source in Heavy-ion Reactions near the Fermi Energies
For central collisions of Ca Ca at 35 MeV/nucleon, the
density and temperature of a fragmenting source have been evaluated in a
self-consistent manner using the ratio of the symmetry energy coefficient
relative to the temperature, , extracted from the yields of primary
isotopes produced in antisymmetrized molecular dynamics (AMD) simulations. The
values are extracted from all isotope yields using an improved
method based on the Modified Fisher Model (MFM). The values of
obtained, using different interactions with different density dependencies of
the symmetry energy term, are correlated with the values of the symmetry
energies at the density of fragment formation. Using this correlation, the
fragment formation density is found to be . Using
the input symmetry energy value for each interaction temperature values are
extracted as a function of isotope mass . The extracted temperature values
are compared with those evaluated from the fluctuation thermometer with a
radial flow correction.Comment: 10 pages, 8 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
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
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