Measurement of radiative α-capture cross sections on 98Ru and 144Sm for γ-process nucleosynthesis

Since p isotopes cannot be produced in neutron-capture reaction networks, a production mechanism via photodisintegration reactions was proposed - the γ process. The specifc path of this reaction network, however, depends strongly on the statistically averaged ratios for proton-, neutron-, and α-decay widths.It was shown in the past, that the uncertainties in the α-decay widths have an impact on the isotopic abundance of the γ-process ashes. Besides systematic studies of the α+nucleus optical-model potential, direct measurements of (α, γ) reaction are needed to reduce the unpredictability of (γ, α) reaction rates.We present preliminary results from direct measurements of the 98Ru(α,γ) and 144Sm(α,γ) cross sections via in-beam measurements at the University of Cologne and the Ruhr-Universitat Bochum and activation experiments at the Physikalisch-Technische Bundesanstalt in Braunschweig and the Technische Universitat Dresden.The in-beam experiment might help to improve our understanding of the γ-process contribution to the p nuclei in the A ~ 100 mass region, while the activation experiment is important for the determination of the initial isotopic abundance ratio of the 146Sm/144Sm chronometer.