Alpha induced reaction cross section measurements on 162Er for the astrophysical gamma process

Abstract

The cross sections of the 162 Er(α,γ) 166 Yb and 162 Er(α,n) 165 Yb reactions have been measured for the first time. The radiative alpha capture reaction cross section was measured from E c.m. = 16.09 down to E c.m. = 11.21 MeV, close to the astrophysically relevant region (which lies between 7.8 and 11.48 MeV at 3 GK stellar temperature). The 162 Er(α,n) 165 Yb reaction was studied above the reaction threshold between E c.m. = 12.19 and 16.09 MeV. The fact that the 162 Er(α,γ) 166 Yb cross sections were measured below the (α,n) threshold at first time in this mass region opens the opportunity to study directly the α-widths required for the determination of astrophysical reaction rates. The data clearly show that compound nucleus formation in this reaction proceeds differently than previously predicted.