Quasicontinuum $\gamma$-decay of ${}^{91,92}$Zr: benchmarking indirect ($n,\gamma$) cross section measurements for the $s$-process

Abstract

Nuclear level densities (NLDs) and $\gamma$-ray strength functions ($\gamma$SFs) have been extracted from particle-$\gamma$ coincidences of the ${}^{92}$Zr($p,p^{\prime }\gamma$)${}^{92}$Zr and ${}^{92}$Zr($p,d\gamma$)${}^{91}$Zr reactions using the Oslo method. The new ${}^{91,92}$Zr $\gamma$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 {\sf TALYS} reaction code, thus serving as a benchmark for this indirect method of estimating ($n,\gamma$) cross sections for Zr isotopes.

arXiv comment10 pages and 9 figures

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• Experimentally constrained ${}^{165,166}\text{Ho}(n,\gamma )$ rates and implications for the $s$ process
• Nuclear Level Density and $\gamma$-ray Strength Function of ${}^{67}\mathrm{Ni}$ and the impact on the i-process
• Extraction of neutron-capture cross sections on ${}^{92}$Zr using the charge-exchange Oslo method
• Nuclear level densities and $\gamma$-ray strength functions of ${}^{87}\mathrm{Kr}$ -- First application of the Oslo Method in inverse kinematics