The recent high-precision measurements of α-particle induced reaction data below the Coulomb barrier (B) make possible the understanding of limits and possible improvement of a previous optical model potential (OMP) for α-particles on nuclei within the mass number range 45≤A≤209 [M. Avrigeanu et al., Phys. Rev. C 82, 014606 (2010)]. An updated version of this potential is given in the present work concerning mainly an increased surface imaginary potential depth well below B for A>130. Moreover, underestimation of reaction cross sections for well-deformed nuclei is removed by using ∼7% larger radius for the surface imaginary part of this spherical OMP. Improved input parameters based on recent independent data, particularly γ-ray strength functions, but no empirical rescaling factor of the γ and/or neutron widths have been involved within statistical model calculation of the corresponding (α, x) reaction cross sections.

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A previously derived semi-microscopic analysis based on the Double Folding Model, for α-particle elastic scattering on A ∼100 nuclei at energies below 32 MeV, is extended to medium mass A ∼50-120 nuclei and energies from ∼13 to 50 MeV. The energy-dependent phenomenological imaginary part for this semi-microscopic optical model potential was obtained including the dispersive correction to the microscopic real potential, and used within a concurrent phenomenological analysis of the same data basis. A regional parameter set for low-energy α-particles entirely based on elastic-scattering data analysis was also obtained for nuclei within the above-mentioned mass and energy ranges. Then, an ultimate assessment of (α, γ), (α, n) and (α, p) reaction cross sections concerned target nuclei from 45 Sc to 118 Sn and incident energies below ∼12 MeV. The former diffuseness of the real part of optical potential as well as the surface imaginary-potential depth have been found responsible for the actual difficulties in the description of these data, and modified in order to obtain an optical potential which describe equally well both the low energy elastic-scattering and induced-reaction data of α-particles.

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