Fusion Process Studied with Pre-equilibrium GDR in TDHF Theory

Cédric Simenel (1, 2) , Philippe Chomaz (2) , Gilles de France (2)

1 DPHN - Département de Physique Nucléaire (ex SPhN)
2 GANIL - Grand Accélérateur National d'Ions Lourds

The equilibration of macroscopic degrees of freedom during the fusion of heavy nuclei, like the charge and the shape, are studied in the Time-Dependent Hartree-Fock theory. The pre-equilibrium Giant Dipole Resonance (GDR) is used to probe the fusion path. It is shown that such isovector collective state is excited in N/Z asymmetric fusion and to a less extent in mass asymmetric systems. The characteristics of this GDR are governed by the structure of the fused system in its pre-equilibrium phase, like its deformation, rotation and vibration. In particular, we show that a lowering of the pre-equilibrium GDR energy is expected as compared to the statistical one. Revisiting experimental data, we extract an evidence of this lowering for the first time. We also quantify the fusion-evaporation enhancement due to gamma-ray emission from the pre-equilibrium GDR. This cooling mechanism along the fusion path may be suitable to synthesize in the future super heavy elements using radioactive beams with strong N/Z asymmetries in the entrance channel.

Keywords: Giant resonances; Hartree-Fock and random-phase approximations; Compound nucleus; Fusion and fusion-fission reactions

Domains: Nuclear Theory [nucl-th]

Cédric Simenel, Philippe Chomaz, Gilles de France. Fusion Process Studied with Pre-equilibrium GDR in TDHF Theory. 2007. ⟨hal-00139795v2⟩