Fragment Production in Peripheral Heavy Ion Collisions at Fermi Energies in Transport Models

Abstract

A study of fragment production in peripheral nuclear collisions at Fermi energies with a transport model (Boltzmann-Nordheim-Vlasov, BNV) is presented. It is compared to an experiment for the reaction 18 O on 181 Ta at E/A = 35 MeV measured at very forward angles. The data are decomposed empirically into a two-component structure, one centered at beam velocity ("direct component") and one at lower velocities ("dissipative component"). It is seen that BNV calculations describe the general features of the dissipative component of the reaction. The direct component of experimental data is interpreted with the Goldhaber model, and the width parameter is extracted. We also include the deexcitation of the excited, primary projectile-like residues due to statistical decay to be able to compare the results of calculations more in detail with experiment. This secondary evaporation is important for both isotope and velocity distributions, but a more consistent estimate of the excitation energy of the residues has to be persued.

Radioactive nuclear beams of COMBAS facility

“…The measurements of total reaction cross sections σ R for weakly bound 6,8 He and 8,9 Li on the nat Al and nat Pb targets at energies (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33) MeV/A were per formed and the results were compared with the previ ous experiments [36,37]. In the range of 10% accu racy there is an agreement with known data.…”

“…Using known present theoretical approaches the direct component was optimal interpreted in the framework of the Goldhaber model [21] and the dissi pative component was analyzed using of the two mod els, namely, Quantum Molecular Dynamics (QMD) [22][23][24] and Boltzmann-Nordheim-Vlasov (BNV) [15,17]. Model analysis showed [25][26][27][28] that the direct component follows the systematic of the Gold haber formalism with a width parameter that is in a reasonable agreement, while the transport description (BNV) of the direct component is not reproduced by the calculations and describes mainly the dissipative component of the experimental spectra. A possible reason is, that BNV includes mean field dynamics and direct nucleon-nucleon (NN) interactions enters only through a collision term.…”

“…In the experiments over the elastic scattering, it is planned to study an evolution of the nucleus shape of unstable nuclei with an increase in the neutron excess for isotopes near N = 20 shell closure, namely, heavy isotopes of elements Ne, [23][24][25][26][27][28][29][30][31][32] Na and Al [42].…”

“…Studies of the cluster structure evolution with increas ing neutron excess in a chain of oxygen isotopes [16][17][18][19][20][21][22][23][24] O are a matter of particular interest, since they can shed light on the experimentally observed instability of oxy gen 26 O and 28 O especially with magic number Z = 8 and neutron number N = 20.…”

“…Two distinct detector systems such as realized Si strip detector telescope and the promising development of the three dimension time projection chamber are discussed. Program of the inves tigations of nuclear reaction mechanisms at intermediate energies of 20-100 MeV/A, measurement of the radii of unstable nuclei, study of the cluster structure of light nuclei near the nuclear drip line and search of 26,28 O resonances in exchange reactions is proposed. The upgrading of experimental facility by the integration of COMBAS separator with the Ion Catcher is discussed.…”