Physics
Scientific paper
Jan 1985
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1985aipc..124..484w&link_type=abstract
AIP Conference Proceedings, Volume 124, pp. 484-503 (1985).
Physics
Inelastic Neutron Scattering, Radiative Capture, 150<=A<=189, Elementary Particle Processes
Scientific paper
Recent measurements of neutron cross sections have provided new data which can be incorporated into models of nucleosynthesis to allow more reliable estimates of the duration and physical conditions under which the heavier chemical elements formed. Measurements of various neutron capture and scattering cross sections for the osmium isotopes have greatly reduced the uncertainty associated with the use of the Re/Os beta decay as a nucleosynthetic chronometer. In particular, measurements of the 189Os(n,n') and 189Os(n,γ) cross sections appear to support the use of the optical model and the Brink-Axel hypothesis to calculate neutron and gamma ray transmission factors needed to estimate the effects of the first excited state in 187Os on neutron capture in a stellar environment. Our latest results imply that the laboratory cross section should be enhanced by about 20% as estimated by Woosley and Fowler and, hence, the age of the chemical elements is estimated to be (17+/-3) byr. Branchings in the s-process path can provide information about the temperature and/or neutron density during nucleosynthesis. Recent measurements of the neutron capture cross sections of the samarium isotopes imply a branch at 147Nd partly bypassing 148Sm. Analysis of this branching yield an estimate for the s-process neutron density of ~108 cm-3.
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