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Summary
This contribution reports on the results of measurements of near- and sub-barrier fusion cross sections in the system 30Si + 30Si performed at the Laboratori Nazionali di Legnaro of INFN. The 30Si beam of the XTU Tandem accelerator in the range Elab= 47-90 MeV, was delivered on a metallic 30Si target (50μg/cm^2) enriched to 99.64% in mass 30, and using the beam electrostatic deflector for the detection of evaporation residues.
The excitation function obtained for this symmetric system has been compared with the previous data on 28Si + 28Si and the Coupled Channels calculations performed using the M3Y+rep. potential, taking into account the low lying 2+ and 3− excitations. The 28Si + 28Si cross sections are largely underestimated at low energies. In a recent work a weak imaginary potential was found to be necessary to fit the data, probably simulating the oblate deformation of this nucleus. On the contrary, the data on 30Si + 30Si are nicely reproduced by the present calculations ( 30Si has a spherical shape).
The slopes of the excitation functions are below the LCS limit even at low measured energies, so that there is no evidence for hindrance. In this representation the cross section difference between the two cases is highlighted. Even above the barrier the two systems behave differently and this is best seen comparing the two barrier distributions where the high energy peak observed for 28Si + 28Si is not found for 30Si + 30Si. This is presumably due to the stronger couplings present in 28Si and this is the object of further theoretical analysis.
