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The cross section of the reaction 112 Sn(α, γ ) 116 Te has been measured in the energy range of astrophysical interest for the p-process. Highly enriched self-supporting 112 Sn foils were bombarded with α beams in the effective center of mass energy range from 7.59 to 11.42 MeV at the Notre Dame FN Tandem Van de Graaff accelerator. The characteristic activity of 116 Te was counted with a pair of large volume Ge clover detectors in close geometry to maximize the detection efficiency. The cross section of the concurrent (α, p) reaction has also been measured. The results are compared with statistical model predictions for different global α-nucleus potentials.

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for converting on the lathe, my blueprints into pieces for the target chamber, and for his valuable help in mechanical issues.Jorge Rocha for doing the lithium implantations and for helping with his expertise in vacuum technology.Eng. Hugo Marques and Prof. Dr. Orlando Teodoro for taking the SIMS and XPS spectra and helping me in the analysis. Palavras chaveLítio primordial, reacções nucleares induzidas por partículas carregadas, secção eficaz, factor astrofísico S , distribuições angulares, blindagem electrónica, modelo de Debye. AbstractThis work presents the results of the experimental study of proton induced nuclear reactions in lithium, namely the He reactions were measured concurrently with seven and four targets, respectively. These targets were produced in order to obtain adequate and stable lithium depth profiles.In metallic environments, the measured electron screening potential energies are much higher than the predictions of atomic-physics models. The Debye screening model applied to the metallic conduction electrons is able to explain these high values. It is a simple model, but also very robust. Concerning primordial nucleosynthesis and stellar evolution models, these v vi results are very important as they show that laboratory measurements are well controlled, and the model inputs from these cross sections are therefore correct.