The Abnormal Threshold Anomaly in the 6Li + 208Pb System

Abstract

Numerous studies have demonstrated that the phenomenological optical potential of tightly bound nuclear systems presents a threshold anomaly phenomenon in the near-Coulomb barrier energy region, where the relationship between the real and imaginary potentials can be well described by the dispersion relation. However, for some weakly bound nuclear systems, the phenomenological optical potential seems to manifest differently, and the dispersion relation struggles to describe the behavior between real and imaginary potentials. Recently, we measured the angular distributions of the transfer reaction 207Pb(7Li,6Li)208Pb in both near and deep barrier energy regions, as well as the elastic scattering angular distributions of the entrance channel 7Li+207Pb. Optical potentials of the 6Li+208Pb system were extracted.The current results indicate that the optical potentials exhibit an abnormal threshold anomaly, and the dispersion relation is not applicable. Possible explanations are discussed, yet further investigations into the underlying physics are required.