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Title: Density reorganization in hot nuclei

Abstract

The density profile of a hot nuclear system produced in intermediate-energy heavy ion collisions is studied in a microcanonical formulation with a momentum and density dependent finite range interaction. The caloric curve and density evolution with excitation are calculated for a number of systems for the equilibrium mononuclear configuration; they compare favorably with the recent experimental data. The studied density fluctuations are seen to build up rapidly beyond an excitation energy of {approx}8 MeV/u indicating the instability of the system toward nuclear disassembly. Explicit introduction of deformation in the expansion path of the heated nucleus, however, shows that the system might fragment even earlier. We also explore the effects of the nuclear equation of state and of the mass and isospin asymmetry on the nuclear equilibrium configuration and the relevant experimental observables.

Authors:
;  [1]; ;  [2]
  1. Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India)
  2. Departament d'Estructura i Constituents de la Materia, Facultat de Fisica, Universitat de Barcelona, Diagonal 647, E-08028 Barcelona (Spain)
Publication Date:
OSTI Identifier:
20995294
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevC.75.054608; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ASYMMETRY; COMPARATIVE EVALUATIONS; CONFIGURATION; DEFORMATION; DENSITY; EQUATIONS OF STATE; EQUILIBRIUM; EXCITATION; FINITE-RANGE INTERACTIONS; FLUCTUATIONS; HEAVY ION REACTIONS; HOT NUCLEI; ISOSPIN; MEV RANGE 01-10

Citation Formats

Samaddar, S. K., De, J. N., Vinas, X., and Centelles, M.. Density reorganization in hot nuclei. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.054608.
Samaddar, S. K., De, J. N., Vinas, X., & Centelles, M.. Density reorganization in hot nuclei. United States. doi:10.1103/PHYSREVC.75.054608.
Samaddar, S. K., De, J. N., Vinas, X., and Centelles, M.. Tue . "Density reorganization in hot nuclei". United States. doi:10.1103/PHYSREVC.75.054608.
@article{osti_20995294,
title = {Density reorganization in hot nuclei},
author = {Samaddar, S. K. and De, J. N. and Vinas, X. and Centelles, M.},
abstractNote = {The density profile of a hot nuclear system produced in intermediate-energy heavy ion collisions is studied in a microcanonical formulation with a momentum and density dependent finite range interaction. The caloric curve and density evolution with excitation are calculated for a number of systems for the equilibrium mononuclear configuration; they compare favorably with the recent experimental data. The studied density fluctuations are seen to build up rapidly beyond an excitation energy of {approx}8 MeV/u indicating the instability of the system toward nuclear disassembly. Explicit introduction of deformation in the expansion path of the heated nucleus, however, shows that the system might fragment even earlier. We also explore the effects of the nuclear equation of state and of the mass and isospin asymmetry on the nuclear equilibrium configuration and the relevant experimental observables.},
doi = {10.1103/PHYSREVC.75.054608},
journal = {Physical Review. C, Nuclear Physics},
number = 5,
volume = 75,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • The method of Albergo, Costa, Costanzo, and Rubbino to determine the temperature and free nucleon density of a disassembling hot nuclear source from fragment yields is modified to include the effects of radial collective flow, generated in the system from compression. We find that the freeze-out density increased substantially whereas the extracted temperature is modified only a little. {copyright} {ital 1997} {ital The American Physical Society}
  • The light charged particles emitted from hot {sup 40}Ca compound nuclei, populated at excitation energy {ital E}{sub {ital x}}=94 MeV and {l angle}{ital J}{r angle}=20.5{h bar} by the reaction 130 MeV {sup 16}O on {sup 24}Mg, have been studied. Energy spectra of protons and alpha particles, measured in coincidence with evaporation residues and with a selection of multiple-alpha chains, have been compared with the predictions of Monte Carlo statistical model calculations. The comparison shows that the level density of hot nuclei with {ital A}{le}40, needed to account for the measured quantities, is well predicted by the Fermi-gas model using amore » level-density parameter {ital a}{sub eff}={ital A}/8 MeV{sup {minus}1} up to excitation energy {l angle}{ital E}{sub th}/{ital A}{r angle}{similar to}1.7 MeV. In agreement with theory, light hot nuclei do not show the transition from {ital a}{sub eff}={ital A}/8 MeV{sup {minus}1} to {ital a}{sub eff}{similar to}{ital A}/13 MeV{sup {minus}1} evidenced in the {ital A}{similar to}160 mass region for the same range of excitation energies {ital E}{sub th}/{ital A}. The analysis of the alpha-particle spectra shows that the effects associated with the angular-momentum-induced deformations depend on the entrance channel characteristics and, in this case, are very small compared with those evidenced in the past for compound nuclei in the region {ital A}=50--70.« less
  • The influence of both quantal and thermal fluctuations on the level-density parameter {ital a} in hot nuclei is investigated. It is found that the large-amplitude motion of the nuclear surface has little influence on {ital a} and that the observed temperature and angular momentum behavior is properly explained through the thermal properties of the energy-dependent effective mass.
  • Macroscopic-microscopic calculations have been performed with the Yukawa folded mean field for 134 spherical even-even nuclei and 6 deformed ones at temperatures 0{<=}T{<=}5 MeV and elongations ranging from oblate shapes to the scission configuration of fissioning nuclei. The Strutinsky type free-energy shell corrections for this sample of nuclei and their temperature and deformation dependence are found by a folding procedure in particle-number space. The average dependence of the single-particle level-density parameter on mass number A and isospin I is determined and compared with previous estimates obtained using the relativistic mean-field theory, the Hartree-Fock approximation with the Skyrme effective interaction, andmore » the phenomenological Thomas-Fermi approach adjusted to experimental data. The estimates for the level-density parameter obtained for different deformations are fitted by a liquid-drop type expression.« less
  • The density and excitation energy dependence of symmetry energy and symmetry free energy for finite nuclei are calculated microscopically in a microcanonical framework, taking into account thermal and expansion effects. A finite-range momentum and density-dependent two-body effective interaction is employed for this purpose. The role of mass, isospin, and equation of state (EOS) on these quantities is also investigated; our calculated results are in consonance with the available experimental data.