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Abstract
The study of reactions induced by exotic weakly bound nuclei at energies around the Coulomb barrier had attracted a large interest in the last decade, since the features of these nuclei can deeply affect the reaction dynamics. The discrimination between different reaction mechanisms is, in general, a rather difficult task. It can be achieved by using detector arrays covering high solid angle and with high granularity that allow to measure the reaction products and, possibly, coincidences between them, as, for example, recently done for stable weakly bound nuclei [1, 2]. We investigated the collision of the weakly bound nucleus 7Be on a 58Ni target at the beam energy of 1.1 times the Coulomb barrier, measuring the elastic scattering angular distribution and the energy and angular distributions of 3He and 4He. The 7Be radioactive ion beam was produced by the facility EXOTIC at INFN-LNL with an energy of 22 MeV and an intensity of ~3×105 pps. Results showed that the 4He yeld is about 4 times larger than 3He yield, suggesting that reaction mechanisms other than the break-up mostly produce the He isotopes. Theoretical calculations for transfer channels and compound nucleus reactions suggest that complete fusion accounts for (41±5%) of the total reaction cross section extracted from optical model analysis of the elastic scattering data, and that 3He and 4He stripping are the most populated reaction channels among direct processes. Eventually estimation of incomplete fusion contributions to the 3,4He production cross sections was performed through semi-classical calculations with the code PLATYPUS [3].
Highlights
The study of reactions induced by stable and unstable weakly bound nuclei at energies around the Coulomb barrier had attracted a large interest in the last decades, since the features of these nuclei can deeply affect the reaction dynamics
In the second study [6], the total reaction cross section was extracted at five energies measuring the elastic scattering angular distribution for the system 7Be+58Ni
The detection system used was DINEX [8]. It consisted of eight Double Sided Silicon Strip Detectors (DSSSDs) arranged in 4 ∆E-E (45+1000 μm) telescopes placed at angles: +57◦, +128◦, -61.5◦, -132◦
Summary
The study of reactions induced by stable and unstable weakly bound nuclei at energies around the Coulomb barrier had attracted a large interest in the last decades, since the features of these nuclei can deeply affect the reaction dynamics. The radioactive and weakly-bound 7Be nucleus has been chosen as subject of our investigation since it has a low particle emission threshold (Sα=1.586 MeV) and a very well pronounced 3He-4He di-nuclear cluster structure. Both of the constituent clusters, that are the main reaction products, are stable charged particles having similar masses. A second energy 17.7±0.5 MeV, was obtained by inserting a degrader along the beam line These energy values correspond to approximately +10% and -10% of the nominal Coulomb barrier for the reaction on a 1 mg/cm thick 58Ni target. It consisted of eight Double Sided Silicon Strip Detectors (DSSSDs) arranged in 4 ∆E-E (45+1000 μm) telescopes placed at angles: +57◦, +128◦, -61.5◦, -132◦
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