M. Jandel

Heavy-residue isoscaling as a probe of the symmetry energy of hot fragments

The isoscaling properties of isotopically resolved projectile residues from peripheral collisions of {sup 86}Kr (25 MeV/nucleon) {sup 64}Ni (25 MeV/nucleon), and {sup 136}Xe (20 MeV/nucleon) beams on various target pairs are employed to probe the symmetry energy coefficient of the nuclear binding energy. The present study focuses on heavy projectile fragments produced in peripheral and semiperipheral collisions near the onset of multifragment emission (E{sup *}/A=2-3 MeV). For these fragments, the measured average velocities are used to extract excitation energies. The excitation energies, in turn, are used to estimate the temperatures of the fragmenting quasiprojectiles in the framework the Fermi gas model. The isoscaling analysis of the fragment yields provided the isoscaling parameters {alpha} that, in combination with temperatures and isospin asymmetries provided the symmetry energy coefficient of the nuclear binding energy of the hot fragmenting quasiprojectiles. The extracted values of the symmetry energy coefficient at this excitation energy range (2-3 MeV/nucleon) are lower than the typical liquid-drop model value {approx}25 MeV corresponding to ground-state nuclei and show a monotonic decrease with increasing excitation energy. This result is of importance in the formation of hot nuclei in heavy-ion reactions and in hot stellar environments such as supernova.

Symmetry energy and the isospin dependent equation of state

We show that the large sequential decay corrections obtained by Ono {it et al} [nucl-ex/0507018], is in contradiction with both the other dynamical and statistical model calculations carried out for the same systems and energy. On the other hand, the conclusion of Shetty {it {et al.}}

Tracing the evolution of the symmetry energy of hot nuclear fragments from the compound nucleus towards multifragmentation

[

Symmetry energy and the isoscaling properties of the fragments produced in Ar 40 , Ca 40 + Fe 58 , Ni 58 reactions at 25, 33, 45, and 53 MeV/nucleon

Phys. Rev. C 70, 011601R (2004)

Measurement of the {sup 157}Gd(n,{gamma}) reaction with the DANCE {gamma} calorimeter array

]

The decay time scale for highly excited nuclei as seen from asymmetrical emission of particles

, that the experimental data favors Gogny

Neutron capture on the s-process branch point nucleus 63Ni

-

Prospects for a measurement of the 237U(n,f) cross section at the LANSCE Lujan Center

AS interaction (obtained assuming a significantly smaller sequential decay effects), is consistent with several other independent studies.

Test of the statistical model in {sup 96}Mo with the BaF{sub 2}{gamma} calorimeter DANCE array

The evolution of the symmetry energy coefficient of the binding energy of hot fragments with increasing excitation is explored in multifragmentation processes following heavy-ion collisions below the Fermi energy. In this work, high-resolution mass spectrometric data on isotopic distributions of projectile-like fragments are systematically compared to calculations involving the statistical multifragmentation model (SMM). Within the SMM picture, the present study suggests a gradual decrease of the symmetry energy coefficient of the hot primary fragments from 25 MeV at the compound nucleus regime towards 15 MeV in the multifragmentation regime. The isotopic distributions of the hot primary fragments are found to be very wide and extend towards the neutron drip line. These findings are expected to have important implications in the modeling of the composition and the evolution of hot and dense astrophysical environments, such as those of core-collapse supernova.

Neutron capture cross section of {sup 241}Am

The symmetry energy and the isoscaling properties of the fragments produced in the multifragmentation of {sup 40}Ar, {sup 40}Ca+{sup 58}Fe, {sup 58}Ni reactions at 25, 33, 45, and 53 MeV/nucleon were investigated within the framework of statistical multifragmentation model. The isoscaling parameters {alpha}, from the primary (hot) and secondary (cold) fragment yield distributions, were studied as a function of excitation energy, isospin (neutron-to-proton asymmetry), and fragment symmetry energy. It is observed that the isoscaling parameter {alpha} decreases with increasing excitation energy and decreasing symmetry energy. The parameter {alpha} is also observed to increase with increasing difference in the isospin of the fragmenting system. The sequential decay of the primary fragments into secondary fragments, when studied as a function of excitation energy and isospin of the fragmenting system, show very little influence on the isoscaling parameter. The symmetry energy, however, has a strong influence on the isospin properties of the hot fragments. The experimentally observed scaling parameters can be explained by symmetry energy that is significantly lower than that for the ground-state nuclei near saturation density. The results indicate that the properties of hot nuclei at excitation energies, densities, and isospin away from the normal ground-state nuclei could be significantly different.