Experimental Reconstruction Of Primary Hot Isotopes And Characteristic Properties Of The Fragmenting Source In Heavy-ion Reactions Near The Fermi Energy

For the first time primary hot isotope distributions are experimentally reconstructed in intermediate heavyion collisions and used with antisymmetrized molecular dynamics(AMD) calculations to determine density, temperature, and symmetry energy coefficient in a self-consistent manner. In this thesis, the characteristic properties of the hot nuclear matter existing at the time of fragment formation in multifragmentation events produced in the reaction 64 Zn + 112 Sn at 40 Me V/nucleon are studied. A kinematical focusing method is employed to determine the multiplicities of evaporated light particles, associated with isotopically identified intermediate-mass fragments. From these data the excitation energies of the primary hot isotopes and the primary isotopic yield distributions are reconstructed using a Monte Carlo method. The extracted excitation energies are in the range of 1 to 4 Me V/nucleon but show a significant decreasing trend as a function of A for a given Z of the isotopes. The results are compared with those of antisymmetrized molecular dynamics(AMD) and statistical multifragmentation model(SMM) simulations. While some of the experimental characteristics are predicted partially by each model, neither simulation reproduces the overall characteristics of the experimental results. The reconstructed yield distributions are in good agreement with the primary isotope distributions obtained from AMD simulations. Utilizing the reconstructed yields and power distribution, characteristic properties of the emitting source are examined. The primary mass distribution exhibits a power-law distribution with the critical exponent A-2.3 for A ≥ 15 isotopes but significantly deviate from that for lighter isotopes. Based on the modified Fisher model, the ratios of the Coulomb and symmetry energy coefficients relative to the temperature, ac/T and asym/T, are extracted as a function of A. The extracted asym/T values are compared with results of the AMD simulations using Gogny interactions with different density dependencies of the symmetry energy term. The calculated asym/T values show a close relation to the symmetry energy at the density at the time of fragment formation. From this relation the density of the fragmenting source is determined to be ρ/ρ0 = 0.63 ± 0.03. Using this density, the symmetry energy coefficient and the temperature of fragmenting source are determined in a self-consistent manner as asym = 24.7 ± 3.4 Me V and T = 4.9 ± 0.2 Me V. Applying the self-consistent method to the other two reaction system, the very similar density and temperature of the fragmenting source for all the three systems indicate that there is a common statistical freeze-out volume at the time of the formation of intermediate mass fragments(IMFs) in AMD transport model.