Influence of the deformation and orientation on the interaction potential of the 28Si+28Si system and its fusion process.

We investigated the orientation behavior of the interaction potential between highly-deformed oblate 2 8 Si nuclei and its influences on the fusion process. The deformed–deformed potential is calculated using the double-folding model based on the realistic M3Y-Reid nucleon–nucleon interaction. We found that the Coulomb barrier parameters and the sub-barrier fusion data strongly depend on the polar orientation angles of the involved deformed nuclei, with a rather less dependence on the azimuthal angles. For interacting oblate nuclei, the elongated configuration corresponding to the lowest Coulomb barrier is obtained at orthogonal polar orientations, while the hexadecapole deformation determines the compact configuration obtained at nonzero polar orientations. The orientation behavior of the Coulomb barrier radius (height and curvature) consistently follow (inversely reflex) the orientation variation of the sum of the half-density radii of the two deformed nuclei, along their centers-of-mass separation vector. The deformations of the colliding nuclei increase their fusion cross-section at sub- and around-barrier energies. The calculations based on the parabolic barrier approximation overestimate the sub-barrier cross-section. The coupled channels calculations with couplings up to the 2 + and 4 + excitation states of 2 8 Si nuclei are needed to reproduce the 2 8 Si + 2 8 Si fusion cross-section, and the corresponding logarithmic slope and barrier distribution, over the full energy region. [ABSTRACT FROM AUTHOR]