Measurement of the $^{77}Se ( n , γ )$ cross section up to 200 keV at the n_TOF facility at CERN

The $^{77}Se ( n , γ )$ reaction is of importance for $^{77}Se$ abundance during the slow neutron capture process in massive stars. We have performed a new measurement of the $^{77}Se$ radiative neutron capture cross section at the Neutron Time-of-Flight facility at CERN. Resonance capture kernels were derived up to 51 keV and cross sections up to 200 keV. Maxwellian-averaged cross sections were calculated for stellar temperatures between $kT=5 \space keV$ and $kT=100\space keV$, with uncertainties between 4.2% and 5.7%. Our results lead to substantial decreases of 14% and 19% in $^{77}Se$ abundances produced through the slow neutron capture process in selected stellar models of $15M⊙$ and $2M⊙$, respectively, compared to using previous recommendation of the cross section.