Stellar ($n,\gamma$) cross section of ${}^{23}$Na

Abstract

The cross section of the ${}^{23}$Na($n,\gamma$)${}^{24}$Na reaction has been measured via the activation method at the Karlsruhe 3.7 MV Van de Graaff accelerator. NaCl samples were exposed to quasistellar neutron spectra at $kT=5.1$ and 25 keV produced via the ${}^{18}$O($p,n$)${}^{18}$F and ${}^7$Li($p,n$)${}^7$Be reactions, respectively. The derived capture cross sections $⟨\sigma {⟩}_{\mathrm{kT}=5keV}=9.1\pm 0.3$ mb and $⟨\sigma {⟩}_{\mathrm{kT}=25keV}=2.03\pm 0.05$ mb are significantly lower than reported in literature. These results were used to substantially revise the radiative width of the first ${}^{23}$Na resonance and to establish an improved set of Maxwellian average cross sections. The implications of the lower capture cross section for current models of $s$-process nucleosynthesis are discussed.

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