Cross-sections at sub-Coulomb energies: Full optical model versus barrier transmission for 40Ca + α

Abstract

Cross-sections for [Formula: see text]Ca + [Formula: see text] at low energies have been calculated from two different models and three different [Formula: see text]-nucleus potentials. The first model determines the cross-sections from the barrier transmission in a real nuclear potential. Second, cross-sections are derived within the optical model (OM) using a complex nuclear potential. The excitation functions from barrier transmission are smooth, whereas the excitation functions from the OM show a significant sensitivity to the chosen imaginary potential. Cross-sections far below the Coulomb barrier are lower from barrier transmission than from the OM. This difference is explained by additional absorption in the tail of the imaginary part of the potential in the OM. At higher energies, the calculations from the two models and all [Formula: see text]-nucleus potentials converge. Finally, in contradiction to another recent study where a double-folding potential failed in a WKB calculation, the applicability of double-folding potentials for [Formula: see text]Ca + [Formula: see text] at low energies is clearly confirmed in the present analysis for the simple barrier transmission model and for the full OM calculation.