skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Isospin dependent thermodynamics of fragmentation

Abstract

The thermal and phase properties of a multifragmentation model that uses clusters as degrees of freedom are explored as a function of isospin. Good qualitative agreement is found with the phase diagram of asymmetric nuclear matter as established by different mean-field models. In particular, from the convexity properties of the nuclear entropy, we show that uncharged finite nuclei display first- and second-order liquid-gas-like phase transitions. Different quantities are examined to connect the thermal properties of the system to cluster observables. In particular, we show that fractionation is only a loose indication of phase coexistence. A simple analytical formula is proposed and tested to evaluate the symmetry (free) energy from the widths of isotopic distributions. Assuming that one may restore the isotopic composition of breakup fragments, it is found that some selected isotopic observables can allow one to quantitatively access the freeze-out symmetry energy in multifragmentation experiments.

Authors:
;  [1]
  1. NIPNE, Bucharest-Magurele, POB-MG 6, Romania and Institut de Physique Nucleaire, IN2P3-CNRS, F-91406 Orsay Cedex (France) and LPC - IN2P3-CNRS/Ensicaen et Universite, F-14050 Caen Cedex (France)
Publication Date:
OSTI Identifier:
20995214
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 4; Other Information: DOI: 10.1103/PhysRevC.75.044605; (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; DEGREES OF FREEDOM; ENTROPY; FRACTIONATION; FRAGMENTATION; FREEZING OUT; ISOSPIN; ISOTOPE RATIO; LIQUIDS; MEAN-FIELD THEORY; NUCLEAR MATTER; PHASE DIAGRAMS; PHASE TRANSFORMATIONS; SYMMETRY; THERMODYNAMICS; WIDTH

Citation Formats

Raduta, Ad. R., and Gulminelli, F. Isospin dependent thermodynamics of fragmentation. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.044605.
Raduta, Ad. R., & Gulminelli, F. Isospin dependent thermodynamics of fragmentation. United States. doi:10.1103/PHYSREVC.75.044605.
Raduta, Ad. R., and Gulminelli, F. Sun . "Isospin dependent thermodynamics of fragmentation". United States. doi:10.1103/PHYSREVC.75.044605.
@article{osti_20995214,
title = {Isospin dependent thermodynamics of fragmentation},
author = {Raduta, Ad. R. and Gulminelli, F.},
abstractNote = {The thermal and phase properties of a multifragmentation model that uses clusters as degrees of freedom are explored as a function of isospin. Good qualitative agreement is found with the phase diagram of asymmetric nuclear matter as established by different mean-field models. In particular, from the convexity properties of the nuclear entropy, we show that uncharged finite nuclei display first- and second-order liquid-gas-like phase transitions. Different quantities are examined to connect the thermal properties of the system to cluster observables. In particular, we show that fractionation is only a loose indication of phase coexistence. A simple analytical formula is proposed and tested to evaluate the symmetry (free) energy from the widths of isotopic distributions. Assuming that one may restore the isotopic composition of breakup fragments, it is found that some selected isotopic observables can allow one to quantitatively access the freeze-out symmetry energy in multifragmentation experiments.},
doi = {10.1103/PHYSREVC.75.044605},
journal = {Physical Review. C, Nuclear Physics},
number = 4,
volume = 75,
place = {United States},
year = {Sun Apr 15 00:00:00 EDT 2007},
month = {Sun Apr 15 00:00:00 EDT 2007}
}
  • The symmetric system {sup 112}Sn+{sup 112}Sn on the neutron poor side will be compared with the neutron rich system {sup 124}Sn+{sup 124}Sn. The measurement of an incident energy of E/A=40 MeV was carried out with a nearly 4 {pi}-coveraged for both, charged particles and neutrons. By varying the mass of this symmetric system without changing the charge we are able to address the isopin dependence of nuclear fragmentation. the correlation of the number emitted charged particles and the number of emitted neutrons will be presented. Impact parameter scales derived from different observables will be discussed. The comparison of the twomore » systems in terms of fragment-production will be investigated.« less
  • The random-phase-approximation formalism with good isospin, developed previously for the particle-hole excitations, is extended to the two-particle and two-hole excitations. It is found that the effect of the isospin symmetry on the normal pairing vibrations is of minor importance. In contrast, the giant pairing vibrations are always split among the isospin components. As an illustration we discuss the experimental results for the /sup 112/Sn(/ital p/,/ital t/) reaction.
  • We use a microscopic approach to derive a schematic Hamiltonian for studying the strengths and the energies of the three components (..delta..T/sub 3/ = +- 1,0) of the dipole excitation. Explicit formulas within the random phase approximation accuracy are given for energies and strengths. A significant isotensor contribution to the isospin splittings is found in agreement with recent experimental data.
  • We investigate separately the isospin effects of Coulomb interaction and symmetry potential on the dissipation and fragmentation in the intermediate energy heavy ion collisions by using isospin-dependent quantum molecular dynamics model. The calculated results show that the Coulomb interaction induces the reductions of both isospin fractionation ratio and nuclear stopping (momentum dissipation). However, the Coulomb interaction not only does not change obviously the strong isospin effect of the symmetry potential on the isospin fractionation ratio but also does not change obviously that of in-medium two-body collision on the nuclear stopping. On the contrary, the symmetry potential induces the enhancement ofmore » the isospin fractionation ratio but it is insensitive to the nuclear stopping. Finally, the competition between the Coulomb interaction and symmetry potential induces the reductions of both isospin fractionation ratio and nuclear stopping for two forms of symmetry potentials in this paper.« less
  • We discuss fragmentation mechanisms, in neutron-rich systems, occurring in central and mid-peripheral collisions at Fermi energies. The most relevant isospin effects are the distillation mechanism, that leads to to the formation of more symmetric fragments, surrounded by a neutron-rich gaseous phase, in central collisions, and isospin transport mechanisms that are responsible for the neutron enrichment of the overlap (neck) region in mid-peripheral collisions, where fragments are formed. The origin of fluctuations in the isotopic composition of fragments and the link to the low density properties of the symmetry energy are discussed.