The s-process branching at W-185

Abstract

The neutron capture cross section of the unstable nucleus W-185 has been derived from experimental photoactivation data of the inverse reaction W-186(gamma, n) W-185. The new result of sigma = 687 +/- 110 mbarn confirms the theoretically predicted neutron capture cross section of W-185 of sigma approximate to 700 mbarn at kT = 30 keV. A neutron density in the classical s-process of n(n) = (3.8(-0.9)(+1.1)) x 10(8) cm(-3) is derived from the new data for the W-185 branching. In a stellar s-process model, one finds a significant overproduction of the residual s-only nucleus Os-186.