Experimental Reconstruction Of Excitation Energies Of Primary Hot Isotopes In Heavy Ion Collisions Near The Fermi Energy

The excitation energies of the primary hot isotopes in multifragmentation events are experimentally reconstructed in the reaction system Zn-64 + Sn-112 at 40 MeV/nucleon. A kinematical focusing method is employed to evaluate the multiplicities of the evaporated light particles associated with isotopically identified fragments with 3 <= Z <= 14. Angular distributions of the velocity spectra of light charged particles and neutrons associated with trigger isotopes are examined. A moving source fit is used to separate the kinematically correlated particles, evaporated from the parents of the detected isotopes, from the uncorrelated particles originating from other sources. The latter are evaluated experimentally relative to those in coincidence with the Li isotopes. A parameter, k, is used to adjust the yield of the uncorrelated particles for different trigger isotopes. For each experimentally detected isotope, the multiplicities, apparent temperatures, and k values for n, p, d, t, and a particles are extracted. Using the extracted values, the excitation energies of the primary hot isotopes are reconstructed employing a Monte Carlo method. The extracted excitation energies are in the range of 1 to 4 MeV/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.