Microscopic optical-model analysis of α-40Ca elastic scattering at 104 MeV through the near/far decomposition

The microscopic α-40Ca optical potential constructed in previous papers is examined with respect to the near/far components of the α elastic scattering cross section at 104 MeV recently extracted from the experimental data. A renormalization of the real part of the potential by a multiplicative constant allows one to reproduce the position of the oscillations of the farside component. However, their amplitude is too weak and the absolute value of the farside component is overestimated. Adding a very weak surface term to the imaginary potential, which was shown to be sufficient to describe the (α, α) elastic scattering and the (3He, α) transfer reaction beyond 100 MeV, improves the absolute value of the farside component but is insufficient to reproduce the amplitude of the oscillations which is shown to be determined by the strength of the imaginary potential. Once the microscopic imaginary potential is modified at small distances the agreement with ''experimental'' near/far components is quite satisfactory. (orig.)