Measurements of 160Dy (p, γ) at Energies Relevant for the Astrophysical γ Process

Rare information on photodisintegration reactions of nuclei with mass numbers A approximate to 160 at astrophysical conditions impedes our understanding of the origin of p-nuclei. Experimental determination of the key (p, gamma) cross sections has been playing an important role in verifying nuclear reaction models and providing rates of relevant (gamma, p) reactions in the gamma process. In this paper we report the first cross-section measurements of Dy-160(p, gamma)Ho-161 and Dy-161(p, n)Ho-161 in the beam energy range of 3.4-7.0 MeV, partially covering the Gamow window. Such determinations are possible by using two targets with various isotopic fractions. The cross-section data can put a strong constraint on the nuclear level densities and gamma strength functions for A approximate to 160 in the Hauser-Feshbach statistical model. Furthermore, we find the best parameters for TALYS that reproduce the available A similar to 160 data, Dy-160(p, gamma)Ho-161 and Er-162(p, gamma)Tm-163, and recommend the constrained Ho-161(gamma, p)Dy-160 reaction rates over a wide temperature range for gamma process network calculations. Although the determined Ho-161(gamma, p) stellar reaction rates at the temperature of 1 to 2 GK can differ by up to one order of magnitude from the NON-SMOKER predictions, it has a minor effect on the yields of Dy-160 and accordingly the p-nuclei, Dy-156,Dy-158. A sensitivity study confirms that the cross section of Dy-160(p, gamma)Ho-161 is measured precisely enough to predict yields of p nuclei in the gamma process.

Automated summary

Rare information on photodisintegration reactions of nuclei with mass numbers A approximate to 160 at astrophysical conditions hinders the understanding of the origin of p-nuclei. Experimental determination of key (p, gamma) cross sections plays a crucial role in verifying nuclear reaction models and providing rates of relevant reactions in the gamma process. The cross-section measurements reported in this study provide important constraints on nuclear level densities and gamma strength functions for nuclei with A approximate to 160, contributing to the refinement of reaction models for the gamma process.