Experimental reconstruction of primary hot isotopes and characteristic properties of the

The characteristic properties of the hot nuclear matter existing at the time of fragment formation in multifragmentation events produced in the reaction 64Zn+Sn112 at 40 MeV/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 primary isotopic yield distributions are reconstructed using a Monte Carlo method. The reconstructed yield distributions are in good agreement with the primary isotope distributions obtained from antisymmetrized molecular dynamics transport model 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 antisymmetrized molecular dynamics 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 MeV and T=4.9±0.2 MeV.