High-precision Sm-144(alpha, alpha)Sm-144 scattering at low energies and the rate of the Sm-144(alpha, gamma)Gd-148 reaction

Background: The alpha-nucleus optical potential plays a crucial role in the calculation of alpha-induced reaction cross sections at low energies in the statistical model which are the basis for the reliable prediction of astrophysical reaction rates. Purpose: The present study attempts to constrain the alpha-nucleus potential for Sm-144 + alpha by the analysis of angular distributions of Sm-144(alpha, alpha) Sm-144 elastic scattering. Methods: Between 20 degrees and 175 degrees complete elastic a scattering angular distributions were measured on the Sm-144 p isotope with high precision at E-lab = 16.13 MeV, at E-lab = 18.07 MeV, and at E-lab = 19.87 MeV. Results: The angular distributions at 18 and at 20 MeV allow a determination of the parameters of the alpha-nucleus potential with small uncertainties, whereas the 16MeV data cannot constrain well these parameters. A prediction of the Sm-144(alpha, gamma) Gd-148 cross section at very low energies from the present fits overestimates the experimental data from literature. Conclusions: The tension between the relatively high cross sections from the analysis of elastic (alpha, alpha) scattering at 16-20 MeV and the low cross sections of the (alpha, gamma) data at deep sub-Coulomb energies around 10 MeV requires further study. The energy gap between the (alpha, alpha) and (alpha, gamma) data can be best filled by new (alpha, n) data.