Trojan Horse Method for the Oxygen-Burning Process Reactions

The O-16 + O-16 fusion reaction is important in terms of the explosive oxygen burning process during late evolution stage of massive stars as well as understanding of the mechanism of low-energy heavy-ion fusion reactions. The astrophysical S factor of such a heavy-ion fusion strongly depends on energy at corresponding stellar temperatures. For the O-16 + O-16 reaction cross section, there are larger discrepancies among di fferent experimental data as the energy decreases, and a complete lack of data below E-c.m. = 7 MeV.We aim to determine the cross sections for the two main exit channels, alpha + 2(8)Si and p + P-31, toward stellar energies. The measurements were performed indirectly by the Trojan horse method (THM) via the O-16(Ne-20, alpha alpha)Si-28 and O-16(Ne-20, p alpha)P-31 three-body reactions, respectively. We performed measurements twice using 20Ne beams at Heavy Ion Laboratory (E-20Ne = 45 MeV) and at Gumilyov Eurasian National University (E-20Ne = 35 MeV). We discuss the applicability of the THM to such a heavy nuclear system showing preliminary results of the momentum distribution of alpha-O-16 intercluster motion in the TH nucleus Ne-20 observed for the first time, which implies a possibility of a multi-step breakup of the TH nucleus.