198,199,200,201,202,204Hg(n, gamma ) cross sections and the termination of s-process nucleosynthesis.

Abstract

The neutron capture cross sections of 198,199,200,201,20 2,204Hg(n,\ensuremath{\gamma}) were measured in the energy range 2.6 to 500 keV. The average capture cross sections were calculated and fitted in terms of strength functions. Resonance parameters for the observed resonances were determined by a shape analysis. Maxwellian averaged capture cross sections were computed for thermal energies kT between 5 and 100 keV. The solar mercury abundance was determined to be 0.34\ifmmode\pm\else\textpm\fi{}0.04 relative to Si${=10}^{6}$. The termination of s-process nucleosynthesis at lead and bismuth was investigated. The abundances of $^{206}$,207,208Pb were reproduced introducing a strong fluence component of the s process in addition to normal s- and r-process nucleosynthesis. The radiogenic $^{207}\mathrm{Pb}$ abundance was determined and the r-process age was calculated via $^{235}\mathrm{U}$. Using Fowler's exponential model, an age T=4.6 Gyr +\ensuremath{\Delta}=17.2\ifmmode\pm\else\textpm\fi{}2.6 Gyr was obtained.