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The nucleosynthesis of the 35 proton-rich nuclei known as "p nuclei'' is described by the so called ''pprocess" mechanism [1]. The latter takes place at explosive stellar environments of temperatures in the range 1.8-3.3×10 K and evolves through a complex sequence of (γ,n), (γ,p) and (γ,α) photodisintegration reactions, along with the inverse capture reactions (n,γ), (p,γ) and (α,γ), followed by β decays or electron capture reactions. All the aforementioned reactions extend within a network of more than 20000 reactions involving about 2000 nuclei in the mass range 12<A<210. In this mass region the experimental data are scarce, as most of the cross sections to be determined are in the μb region due to Coulomb barrier penetration. Consequently, the determination of almost all reaction rates has to rely on cross sections calculated by the nuclear reaction theory of Hauser-Feshbach (HF) [2]. At p-process sites the α-particles contributing in the nucleosynthesis are found with energies of a few MeV, within the so-called Gamow Window, far below the Coulomb barrier. At such low energies the α-induced HF cross sections are governed by the a-particle transmission coefficient which is determined by solving the Schrodinger equation using the appropriate Optical Model Potential (OMP). Therefore the a-particle OMP plays a significant role in the explanation of the observed in the solar system p-nuclei abundances that are the imprints of the p-process mechanism. Aiming at determining a global α-particle OMP that is able to reproduce accurately all existing experimental data, over the whole mass region, several models have been developed so far. The range of the different models defines the uncertainty level up to which global α-particle induced reactions cross sections can be predicted. The measurement and comparison of experimental cross-section data is of great importance in order to constrain the determination of a global α-particle OMP. Additional experimental data at astrophysically relevant energies are required, especially for radioactive capture reactions at high mass regions (A>100). In this context, the present work reports on the measurement of the cross section of the reactions Ni(α,γ)Zn, Zn(α,γ)Ge, Pd(α,γ)Cd and Cd(α,γ)Sn.

Systematic cross section measurements of (α,γ) reactions for astrophysics