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

M Guttormsen,H K Toft,A Görgen,A V Voinov,S Goriely,G Tagliente,H Utsunomiya,T W Hagen,T Renstrøm,K Wikan,S Siem,A C Larsen,N U H Syed

doi:10.1007/978-3-030-13876-9_65

Abstract

Nuclear level densities (NLDs) and $\gamma $-ray strength functions ($\gamma $SFs) of $^{91,92}$Zr have been extracted from particle-$\gamma $ coincidences using the Oslo method. The extracted $\gamma $SF data, combined with photonuclear cross sections, cover the whole energy range from $E_{\gamma } \approx 1.5$ MeV up to the giant dipole resonance at $E_{\gamma } \approx 17$ MeV. The wide-range $\gamma $SF data display structures at $E_{\gamma } \approx 9.5$ MeV, compatible with a superposition of the spin-flip M1 resonance and a pygmy E1 resonance. Furthermore, the $\gamma $SF shows a minimum at $E_{\gamma } \approx $ 2–3 MeV and an increase at lower $\gamma $-ray energies. The experimentally constrained NLDs and $\gamma $SFs are shown to reproduce known ($n, \gamma $) 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, \gamma $) cross sections for Zr isotopes.

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