Indirect $$(n, \gamma )^{91,92}$$ Zr Cross Section Measurements for the s-Process

Abstract

Nuclear level densities (NLDs) and γ-ray strength functions (γ SFs) have been extracted from particle-γ coincidences of the 92 Zr(p,p γ) 92 Zr and 92 Zr(p,dγ) 91 Zr reactions using the Oslo method. The new 91,92 Zr γ SF data, combined with photonuclear cross sections, cover the whole energy range from E γ ≈ 1.5 MeV up to the giant dipole resonance at E γ ≈ 17 MeV. The wide-range γ SF data display structures at E γ ≈ 9.5 MeV, compatible with a superposition of the spin-flip M1 resonance and a pygmy E1 resonance. Furthermore, the γ SF shows a minimum at E γ ≈ 2-3 MeV and an increase at lower γ-ray energies. The experimentally constrained NLDs and γ SFs are shown to reproduce known (n,γ) and Maxwellian-averaged cross sections for 91,92 Zr using the TALYS reaction code, thus serving as a benchmark for this indirect method of estimating (n,γ) cross sections for Zr isotopes.