Study of the Threshold Anomaly in the Scattering of Li Isotopes on 27Al

Angular distributions of 6,7Li scattered by 27Al have been measured at different bombarding energies between 6 and 18 MeV. The results obtained from an optical model analysis using several potentials indicate that there is an isotopic dependence in the energy variation of the real and imaginary strengths. Whereas the 7Li + 27Al system shows no indication of any threshold anomaly, the 6Li + 27Al reaction suggests the presence of the so-called breakup threshold anomaly.