Naslov
Fusion hindrance for the positive Q-value system 12C+30

Autori
Montagnoli, G. ; Stefanini, A. M. ; Jiang, C. L. ; Hagino, K. ; Galtarossa, F. ; Colucci, G. ; Bottoni, S. ; Broggini, C. ; Caciolli, A. ; Čolović, Petra ; Corradi, L. ; Courtin, S. ; Depalo, R. ; Fioretto, E. ; Fruet, G. ; Gal, A. ; Goasduff, A. ; Heine, M. ; Hu, S. P. ; Kaur, M. ; Mijatović, Tea ; Mazzocco, M. ; Montanari, D. ; Scarlassara, F. ; Strano, E. ; Szilner, Suzana ; Zhang, G. X.

Izvornik
Physical review. C (2469-9985) 97 (2018), 2; 024610, 6

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
nuclear reaction ; nuclear fusion

Sažetak
Background: The fusion reaction 12C+30Si is a link between heavier cases studied in recent years, and the light heavy-ion systems, e.g., 12C+12C, 16O+16O that have a prominent role in the dynamics of stellar evolution. 12C+30Si fusion itself is not a relevant process for astrophysics, but it is important to establish its behavior below the barrier, where couplings to low-lying collective modes and the hindrance phenomenon may determine the cross sections. The excitation function is presently completely unknown below the barrier for the 12C+30Si reaction, thus no reliable extrapolation into the astrophysical regime for the C+C and O+O cases can be performed. Purpose: Our aim was to carry out a complete measurement of the fusion excitation function of 12C+30Si from well below to above the Coulomb barrier, so as to clear up the consequence of couplings to low-lying states of 30Si, and whether the hindrance effect appears in this relatively light system which has a positive Q value for fusion. This would have consequences for the extrapolated behavior to even lighter systems. Methods: The inverse kinematics was used by sending 30Si beams delivered from the XTU Tandem accelerator of INFN-Laboratori Nazionali di Legnaro onto thin 12C (50μg/cm2) targets enriched to 99.9% in mass 12. The fusion evaporation residues (ER) were detected at very forward angles, following beam separation by means of an electrostatic deflector. Angular distributions of ER were measured at Ebeam=45, 59, and 80 MeV, and they were angle integrated to derive total fusion cross sections. Results: The fusion excitation function of 12C+30Si was measured with high statistical accuracy, covering more than five orders of magnitude down to a lowest cross section ≃3μb. The logarithmic slope and the S factor have been extracted and we have convincing phenomenological evidence of the hindrance effect. These results have been compared with the calculations performed within the model that considers a damping of the coupling strength well inside the Coulomb barrier. Conclusions: The experimental data are consistent with the coupled-channels calculations. A better fit is obtained by using the Yukawa-plus-exponential potential and a damping of the coupling strengths inside the barrier. The degree of hindrance is much smaller than the one in heavier systems. Also a phenomenological estimate reproduces quite closely the hindrance threshold for 12C+30Si, so that an extrapolation to the C+C and O+O cases can be reliably performed.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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