Experimental determination of the neutron resonance peak of Er 162 at 67.8 eV

Er162 is one of the p nuclei in nuclear astrophysics, and its (n,γ) cross sections are important input parameters in nuclear astrophysics network calculations. Resonance data for Er162(n,γ)Er163 at 67.8 eV is currently not present in the EXFOR database; however, it is included in the ENDF/B VIII.0 database. The (n,γ) cross section of Ernat has been measured in the energy range of 1-100 eV at the Back-n facility in the China Spallation Neutron Source. However, due to the influence of the in-beam γ background of the Back-n Facility, it is has not been possible to observe the neutron resonance peak of Er162 at 67.8 eV. A general simulation method is proposed for quantifying the in-beam γ-ray background. By subtracting the in-beam γ-ray background, the neutron-capture yields of Er162 are obtained within the energy range of 20-100 eV. The neutron resonance parameters of Er162 at 67.8 eV are then extracted successfully. It is found that Γγ=101.15±10.08 meV and Γn=2.79±0.28 meV, which are consistent with the ENDF/B VIII.0 database. However, the 51.4-eV resonance peak of Er162(n,γ) is currently unobserved.