(70)Ge(p,gamma)(71)As and (76)Ge(p,n)(76)As cross sections for the astrophysical p process : Sensitivity of the optical proton potential at low energies

The cross sections of the (70)Ge(p,gamma)(71)As and (76)Ge(p,n)(76)As reactions have been measured with the activation method in the Gamow window for the astrophysical p process. The experiments were carried out at the Van de Graaff and cyclotron accelerators of ATOMKI. The cross sections have been derived by measuring the decay gamma-radiation of the reaction products. The results are compared to the predictions of Hauser-Feshbach statistical model calculations using the code NON-SMOKER. Good agreement between theoretical and experimental S factors is found. Based on the new data, modifications of the optical potential used for low-energy protons are discussed.