The cross sections of 14N(n,p)14C at stellar energies and its role as a neutron poison for S-process nucleosynthesis

The absolute average cross section <σ> of the 14N(n,p)14C reaction has been measured using neutron spectra that closely resemble Maxwell-Boltzmann distributions with thermal energies of kT = 25.0 and 52.4 keV: <σ> = 0.81±0.05 and 0.52±0.06 mb, respectively. The resulting reaction rates are nearly the same at T9 = 0.29 and 0.61, and their average, NA<συ> = 1.3±0.1)x105 cm3s-1mol-1, is about a factor of three smaller than the previously adopted values obtained by extrapolation between thermal and higher-energy data. Thus, the 14N(n,p)14C reaction plays a correspondingly smaller role as a neutron poison for s-process nucleosynthesis. (orig.)