Photonuclear Reaction Rates of 157,159Ho and 163,165Tm and Their Impact in the γ-process

Abstract

Reliable photonuclear reaction rates in stellar conditions are essential for understanding the origin of the heavy stable neutron-deficient isotopes between 74Se and 196Hg, i.e., p-nuclei. However, many reaction rates of relevance still have to rely on the Hauser–Feshbach (HF) model due to the rarity of experimental progress. One such case is in the mass range of 160 for Dy, Er, Ho, and Tm isotopes. In this work we attempt to constrain the HF model in the TALYS package by reproducing the available experimental data on 160Dy(p, γ)161Ho and 162Er(p, γ)163Tm in the A ∼ 160 mass region, and examine the effects of level density, gamma strength function, and the optical model potential. The constrained model then allows us to calculate the reaction rates of 157,159Ho(γ, p) and 163,165Tm(γ, p) for the γ-process nucleosynthesis in a carbon-deflagration model for Type Ia supernovae. Our recommended rates differ from the JINA REACLIB by more than one order of magnitude in the temperature range 2–3 GK. This results in changes in the final abundance of p-nuclei in the A ∼ 160 mass range by −5.5% to 3% from those with JINA, which means that the uncertainty of (γ, p) reactions is not predominant for the synthesis of these nuclei.