New Studies of the Dynamical Dipole in Asymmetric Heavy-Ion Reactions: A Probe of the Nuclear Equation of State

In heavy-ion nuclear reactions the process leading to complete fusion is expected to produce pre-equilibrium gamma-ray emission, called dynamical dipole ( DD), when particular conditions are met. Indeed, when there is an N/Z asymmetry between projectile and target, charge equilibration takes place with a collective dipole oscillation associated to a gamma-ray emission. The existing experimental data concerning this pre-equilibrium gamma-ray emission are still rather scarce and manly concentrated in the A similar or equal to 132 mass region. It is important to point out that the model, used to compared the data, critically depends on the nuclear equation of state with its symmetry term. The very preliminary results concerning the measurement of the DD gamma-ray emission in the fusion reaction O-16 (E-lab = 192 MeV) + Sn-116 at 12 MeV/u will be presented. The experiment aims at the measurement of the total emission yield of the DD at 12 MeV/u where the predicted theoretical yield does not completely reproduce the experimental data. The experiment has been performed at the INFN Legnaro Laboratories using the GARFIELD-HECTOR array.