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Background: alpha-nucleus potentials play an essential role for the calculation of alpha-induced reaction cross sections at low energies in the statistical model. Uncertainties of these calculations are related to ambiguities in the adjustment of the potential parameters to experimental elastic scattering angular distributions and to the energy dependence of the effective alpha-nucleus potentials.

The total cross sections for the Gd-152(p,gamma)Tb-153 and Gd-152(p, n)Tb-152 reactions have been measured by the activation method at effective center-of-mass energies 3.47

Background: Astrophysical reaction rates, which are mostly derived from theoretical cross sections, are necessary input to nuclear reaction network simulations for studying the origin of p nuclei. Past experiments have found a considerable difference between theoretical and experimental cross sections in some cases, especially for (alpha,gamma) reactions at low energy. Therefore, it is important to experimentally test theoretical cross section predictions at low, astrophysically relevant energies.

Background: The gamma process in supernova explosions is thought to explain the origin of proton-rich isotopes between Se and Hg, the so-called p nuclei. The majority of the reaction rates for gamma process reaction network studies have to be predicted in Hauser-Feshbach statistical model calculations using global optical potential parametrizations. While the nucleon+nucleus optical potential is fairly well known, for the alpha+nucleus optical potential several different parametrizations exist and large deviations are found between the predictions calculated using different parameter sets.

Background: The. process in core-collapse supernova explosions is thought to explain the origin of proton-rich isotopes between Se and Hg, the so-called p nuclei. The majority of the reaction rates for gamma process reaction network studies has to be predicted in Hauser-Feshbach statistical model calculations. Recent investigations have shown problems in the prediction of alpha widths at astrophysical energies. This impacts the reliability of abundance predictions in the upper mass range of the p nuclei.

In order to extend the experimental database relevant for the astrophysical gamma-process towards the unexplored heavier mass region, the cross sections of the Eu-151(alpha, gamma)Tb-155 and Eu-151 (alpha, n)Tb-154 reactions have been measured at low energies between 12 and 17 MeV using the activation technique. The results are compared with the predictions of statistical model calculations and it is found that the calculations overestimate the cross sections by about a factor of 2. A sensitivity analysis shows that this discrepancy is caused by the inadequate description of the alpha+nucleus channel. A factor of 2 reduction of the reaction rate of Eu-151(alpha, gamma)Tb-155 in gamma-process network calculations with respect to theoretical rates using the optical potential by McFadden and Satchler (1966 Nucl. Phys. 84 177) is recommended.