Shape resonances and singularities of the proton optical potential in the sub-Coulomb energy region

Optical cross sections and strength functions are calculated in a wide range of A = 40--130 and E = 3--10 MeV with the aim to understand the anomalous behavior of the proton optical potential (OP) in the sub-Coulomb region in the proximity of shape resonances. The sensitivity of the results to the OP parameter variation is determined. Regions (of A and E) on the slopes of shape resonances are discovered where the chi2 fit can lead to unphysical anomalies in the OP. The dependence of the depth of the well V/sub R/ on the orbital angular momentum l is considered as a possible reason for discrepancy between experiment and theory in the shape-resonance region for l = 0, 1, 2, and 3