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        Neutron capture reaction rates for silicon and their impact on the origin of presolar mainstream SiC grains

        Author
        Guber, K. H.
        Koehler, P. E.
        Derrien, H.
        Valentine, T.E.
        Leal, L.C.
        Sayer, R.O.
        Rauscher, T.
        Attention
        2299/11010
        Abstract
        We have made new, improved measurements of the Si28-30 (n, gamma) cross sections and have done a resonance analysis of these data including previous total cross sections. Together with the calculated contributions due to direct capture, we calculated the astrophysical (n, gamma) reaction rates and investigated the s-process abundances of the Si isotopes. Measured isotopic anomalies of intermediate and heavy elements in SiC grains from meteorites appear to be attributable to the s-process in asymptotic giant branch (AGB) stars. But the Si isotopic ratios in these grains are substantially different than s-process models predict. Therefore, recent papers have invoked galactic chemical evolution or other effects to explain the Si isotope ratios in these grains. Our new reaction rates are significantly different than previous rates, and s-process calculations using these rates lead to much larger isotopic shifts in Si-30. However, these exploratory calculations demonstrate that even with these substantially different rates the large observed variation in SiC grain from AGB stars cannot be explained by standard s-process models.
        Publication date
        2003-06
        Published in
        Physical Review C
        Published version
        https://doi.org/10.1103/PhysRevC.67.062802
        Other links
        http://hdl.handle.net/2299/11010
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