Elastic and inelastic scattering in the 6Li, 9Be + 12C systems: excitation of unbound excited states and cluster transfers

For the system 9Be + 12C, angular distributions at Ec.m.= 10.86 MeV and excitation functions in the c.m. energy range 3-16 MeV have been measured for the elastic scattering and inelastic scattering leading to the unbound state 9Be(5/2-, 2.43 MeV) and to the state 12C(2+, 4.44 MeV). For the system 6Li + 12C, angular distributions at Ec.m.= 13.33 MeV and excitation functions in the c.m. energy range 2-16 MeV have been measured for the elastic scattering and inelastic scattering leading to the unbound state 6Li(3+, 2.186 MeV) and to the state 12C(2+, 4.44 MeV). The wide angular range of the inelastic-scattering angular distributions, 20 circle < or ∼θc.m. < or ∼170 circle, is obtained by changing appropriately the roles of the projectile and target nuclei. The 9Be + 12C data are analyzed using first-order EFR-DWBA calculations that include 3He-cluster transfers in order to describe the enhancement in the elastic and inelastic scattering at backward scattering angles. In addition to the 3He transfers, compound-nucleus contributions are found also to be significant at the backward scattering angles. Reorientation and coupling effects in the 9Be + 12C system are studied using an optical potential with a double-folded real part, resulting in a good description of the 9Be(5/2-, 2.43 MeV) angular distribution without the need for a renormalisation of the M3Y nucleon-nucleon interaction, but with the elastic 3He transfer still required to account for the backward-angle enhancement in the elastic-scattering angular distribution. The 6Li + 12C data are analyzed using coupled-channels calculations; here the inclusion of compound-nucleus contributions is found to be significant for inelastic scattering at backward scattering angles. (orig.)