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 E_c.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 E_c.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 to the unbound state ⁶Li(3 ⁺, 2.186 MeV) and to the state ¹²C( ⁺, 4.44 MeV). The wide angular range of the inelastic-scattering angular distributions, 20° ≲ θ_c.m.≲ 170°, 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.