Study On Transverse Flow Mass Dependence And The Fragmenting Source Properties In Heavy-ion Reactions At Intermediate Energies

The investigations of heavy-ion collisions at intermediate energy region are of intrinsic interest to provide important information on the reaction mechanism, the nuclear matter properties, the nuclear equation of state(Eo S), the symmetry energy, etc.. In this thesis, the mechanism of the mass dependence of transverse flow and the characteristic properties of the fragmenting source in heavy-ion reactions at intermediate energy region were studied. The main results and conclusions are as the following:(a) Mass dependence of transverse flow in heavy-ion reactions at intermediate energy region. The mass dependence of the transverse flow in the reactions of 40 Ca + 40 Ca at 35 Me V/nucleon has been experimentally determined for emitted isotopes with Z = 1 to 9. The observed flow was compared with that calculated using a Constrained Molecular Dynamics(Co MD) simulation. With the application of the appropriate experimental filter, the general trend of the experimental mass dependent flow is well reproduced by the simulation employing an effective interaction corresponding to a soft Eo S(K = 200 Me V). The Co MD events were further utilized to study the mechanism of generation of the mass dependent flow. It is found that the mass dependent flow is generated by the interplay between the thermal and collective motions under the momentum conservation in the fragmenting system. With the help of the Collective-Thermal Interplay Model(CTIM), the mass dependent flow scaled by the reduced mass of fragments A/Asys is found to be almost independent on the size of the system.(b) Characteristic properties of the fragmenting source in heavy-ion reactions at intermediate energy region. For central collisions of 40 Ca + 40 Ca at 35 Me V/nucleon, the density and temperature of a fragmenting source have been evaluated in a self-consistent manner using the ratio of the symmetry energy coefficient relative to the temperature, asym/T, extracted from the yields of primary isotopes produced in antisymmetrized molecular dynamics(AMD) simulations. The asym/T values were extracted from all isotope yields using an improved method based on the Modified Fisher Model(MFM). The values of asym/T obtained, using different interactions with different density dependencies of the symmetry energy term, were correlated with the values of the symmetry energies at the density of fragment formation. Using this correlation, the fragment formation density was found to be ρ/ρ0 = 0.67 ± 0.02. Using the input symmetry energy value for each interaction, the apparent temperature values were extracted and a mass dependent behavior of the extracted apparent temperature values was observed. The temperature of the fragmenting source was finally determined as T = 5.5 ± 0.2 Me V after iterations. Using the experimentally reconstructed hot isotope yields for multifragmentation events in the reaction system 64 Zn + 112 Sn at 40 Me V/nucleon, the density of the fragmenting source was extracted as ρ/ρ0 = 0.65 ± 0.02 in a self-consistent manner. Comparing with that of the AMD simulations, T = 5.0 ± 0.4 Me V and asym = 23.1 ± 0.6 Me V were evaluated for the fragmenting system experimentally observed in the reaction studied.