Neutron capture cross section ofO18and its astrophysical implications

The neutron capture rate on $^{18}\mathrm{O}$ is of considerable interest in the interpretation of nucleosynthesis in inhomogeneous big bang scenarios and for stellar helium burning in massive red giant stars as well as AGB stars. We measured the reaction cross section of $^{18}\mathrm{O}$(n,\ensuremath{\gamma}${)}^{19}$O at the Forschungszentrum Karlsruhe with a fast cyclic neutron activation technique at laboratory neutron energies of 25, 129, 152, 250, and 370 keV. Direct capture and shell model calculations were performed to interpret the results as well as previous unpublished data. Contributions to the reaction cross section and to the new stellar reaction rate will be discussed. \textcopyright{} 1996 The American Physical Society.