Effects of uncertainties of the 22Ne(α, n)25Mg and 13C(α, n)16O reaction rates in the s-process yields

In the low mass star AGB phase the region between H shell and He shell (He-intershell) is affected by brief convective instabilities (Thermal Pulses), due to trigger of the He burning in the He shell. In this conditions the neutron source Ne-22(alpha, n) Mg-25 is marginally activated (releasing a short neuton burst with a peak neutron density n(n) < 10(10) n cm(-3)), and may change isotopic ratios near s-path branchings sensitive to the peak neutron density. For each element we analyse the isotopic ratios obtained in the AGB nucleosynthesis model using three different Ne-22(alpha, n) Mg-25 rates: first,with the "standard rate", evaluated in [I]; second, with the standard rate multiplied by a factor of two, and third, the standard rate divided by a factor of two. This factor is close to the present uncertainty factor of the Ne-22(alpha,n)Mg-25 rate. The same analysis is presented for C-13 (alpha, n) O-16 reaction rate, the primary neutron source in the He-intershell, which works in radiative conditions in a thin region in the top layers of the He-intershell (C-13-pocket) during interpulse periods. In this case the standard rate is evaluated in [2].