Cross section and reaction rate of image determined from thick target yield measurements

For the better understanding of the astrophysical γ-process the experimental determination of low energy proton- and α-capture cross sections on heavy isotopes is required. The existing data for the image reaction are contradictory and strong fluctuation of the cross section is observed which cannot be explained by the statistical model. In this paper a new determination of the image and image cross sections based on thick target yield measurements are presented and the results are compared with existing data and model calculations. Reaction rates of image at temperatures relevant for the γ-process are derived directly from the measured thick target yields. The obtained rates are a factor of 2 lower than the ones used in astrophysical network calculations. It is argued that in the case of fluctuating cross sections the thick target yield measurement can be more suited for a reliable reaction rate determination.