Monday·May 11, 2015

[Submitted on 8 May 2015] (cross-list from nucl-ex)

Oscillations above the barrier in the fusion of 28Si + 28Si

G. Montagnoli · A. M. Stefanini · H. Esbensen · L. Corradi · S. Courtin · E. Fioretto · J. Grebosz · F. Haas · H. M. Jia · C. L. Jiang · M. Mazzocco · C. Michelagnoli and 7 other authors

Fusion cross sections of 28Si + 28Si have been measured in a range above the barrier with a very small energy step (DeltaElab = 0.5 MeV). Regular oscillations have been observed, best evidenced in the first derivative of the energy-weighted excitation function. For the first time, quite different behaviors (the appearance of oscillations and the trend of sub-barrier cross sections) have been reproduced within the same theoretical frame, i.e., the coupled-channel model using the shallow M3Y+repulsion potential. The calculations suggest that channel couplings play an important role in the appearance of the oscillations, and that the simple relation between a peak in the derivative of the energy-weighted cross section and the height of a centrifugal barrier is lost, and so is the interpretation of the second derivative of the excitation function as a barrier distribution for this system, at energies above the Coulomb barrier.