1,024 research outputs found
Isospin diffusion in semi-peripheral + collisions at intermediate energies (II): Dynamical simulations
We study isospin effects in semi-peripheral collisions above the Fermi energy
by considering the symmetric + and the asymmetric reactions
+ over the incident energy range 52-74 A MeV. A
microscopic transport model with two different parameterizations of the
symmetry energy term is used to investigate the isotopic content of
pre-equilibrium emission and the N/Z diffusion process. Simulations are also
compared to experimental data obtained with the INDRA array and bring
information on the degree of isospin equilibration observed in Ni + Au
collisions. A better overall agreement between data and simulations is obtained
when using a symmetry term which linearly increases with nuclear density
Comparison of fragment partitions production in peripheral and central collisions
Ensembles of single-source events, produced in peripheral and central
collisions and correponding respectively to quasi-projectile and quasi-fusion
sources, are analyzed. After selections on fragment kinematic properties,
excitation energies of the sources are derived using the calorimetric method
and the mean behaviour of fragments of the two ensembles are compared.
Differences observed in their partitions, especially the charge asymmetry, can
be related to collective energy deposited in the systems during the collisions.Comment: 7 pages, 2 figures, presented at the International Workshop on
Multifragmentation and Related Topics, Caen France, 4-7th november 2007
(IWM2007
Break-up fragments excitation and the freeze-out volume
We investigate, in microcanonical multifragmentation models, the influence of
the amount of energy dissipated in break-up fragments excitation on freeze-out
volume determination. Assuming a limiting temperature decreasing with nuclear
mass, we obtain for the Xe+Sn at 32 MeV/nucleon reaction [J. D. Frankland et
al., Nucl. Phys. A689, 905 (2001); A689, 940 (2001)] a freeze-out volume almost
half the one deduced using a constant limiting temperature.Comment: 11 pages, 6 figure
Kinetic energy spectra for fragments and break-up density in multifragmentation
We investigate the possibility, in nuclear fragmentation, to extract
information on nuclear density at break-up from fragment kinetic energy spectra
using a simultaneous scenario for fragment emission. The conclusions we derive
are different from the recently published results of Viola et al. [Phys. Rev.
Lett. 93, (2004), 132701] assuming a sequential fragment emission and claiming
that the experimentally observed decrease of peak centroids for kinetic energy
spectra of fragments with increasing bombarding energy is due to a monotonic
decrease of the break-up density.Comment: 6 pages, 3 figure
Break-up stage restoration in multifragmentation reactions
In the case of Xe+Sn at 32 MeV/nucleon multifragmentation reaction break-up
fragments are built-up from the experimentally detected ones using evaluations
of light particle evaporation multiplicities which thus settle fragment
internal excitation. Freeze-out characteristics are extracted from experimental
kinetic energy spectra under the assumption of full decoupling between fragment
formation and energy dissipated in different degrees of freedom. Thermal
kinetic energy is determined uniquely while for freeze-out volume - collective
energy a multiple solution is obtained. Coherence between the solutions of the
break-up restoration algorithm and the predictions of a multifragmentation
model with identical definition of primary fragments is regarded as a way to
select the true value. The broad kinetic energy spectrum of He is
consistent with break-up genesis of this isotope.Comment: 17 pages, 5 figure
- …