The s-Process Branching at 185W

The neutron capture cross section of the unstable nucleus 185W has been derived from experimental photoactivation data of the inverse reaction 186W(γ, n)185W. The new result of σ = 687 ± 110 mbarn confirms the theoretically predicted neutron capture cross section of 185W of σ ≈ 700 mbarn at kT = 30 keV. A neutron density in the classical s-process of nn = × 108 cm-3 is derived from the new data for the 185W branching. In a stellar s-process model, one finds a significant overproduction of the residual s-only nucleus 186Os.