Neutron scattering in sup 189 Os for nucleosynthesis rates of the odd- A Os isotopes and nucleochronology

Neutron elastic and inelastic scattering cross sections have been determined for neutrons incident on {sup 189}Os at three very low energies. Cross sections for scattering to the ground state and 36.2-keV excited level have been measured for incident energies of 63.5 and 73.3 keV, and also to the 69.6-keV excited level at 97.5-keV incident energy. These measurements are combined with neutron scattering cross sections for {sup 187}Os, neutron capture cross sections, and other low-energy scattering observables to provide a basis for a single, consistent model of all data for both odd-{ital A} Os isotopes. The properly interpreted capture rates are important for the Re/Os nucleochronology and for {ital s}-process nucleosynthesis rates. The elastic and inelastic scattering cross sections provide a very-low-energy test of statistical model-flux distributions; model accuracy at very low energies is an important issue for reaction rates used in nucleosynthesis estimates.