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.

10 pages and 9 figures

References in corpus (5)

• The r-process of stellar nucleosynthesis: Astrophysics and nuclear physics achievements and mysteries
• Analysis of possible systematic errors in the Oslo method
• Novel technique for constraining r-process (n,$\gamma$) reaction rates
• The SiRi Particle-Telescope System
• Large low-energy $M1$ strength for ${}^{56,57}$Fe within the nuclear shell model

Cited by in corpus (1)

• Nuclear level densities and gamma-ray strength functions of ${}^{180,181,182}$Ta