Threshold anomalies in 9Be + 12C

The extended optical model is used to simultaneously analyze the elastic scattering and fusion data for the weakly-bound system of ⁹Be + ¹²C in the low-energy region. Dynamic polarization potentials $U_F$, $U_D$, associated with fusion and direct couplings, respectively, are introduced. Corresponding fitting parameters leading to dispersive potentials are found, which provide good simultaneous descriptions of elastic and fusion data. The energy-dependent behavior of the polarization potentials establishes a striking difference with respect to that observed for weakly bound projectiles, including ⁹Be, on medium- and heavy-mass targets. Contrary to similar analyses made on weakly-bound systems, the real part of $U_D$ is found to be attractive in the present case. The observed behavior is discussed.