We report a new measurement of the photoneutron cross section for ${}^{89}\mathrm{Y}(\gamma ,n){}^{88}\mathrm{Y}$ in the energy range of 11.85–18.70 MeV at the Shanghai Laser Electron Gamma Source (SLEGS) using a neutron Flat-Efficiency Detector (FED) array. An iterative unfolding algorithm was combined to extract monoenergetic cross sections with a typical total uncertainty $\sim 3.5\%$. Then the new experimental results are systematically compared with the data from Saclay, Livermore and IAEA/PD-2019, which implies the reliability of our results. Based on the new experimental results, the $\gamma$-ray strength function ($\gamma \mathrm{SF}$) was deduced and used as input for Hauser-Feshbach calculations of the inverse reaction ${}^{88}\mathrm{Y}(n,\gamma ){}^{89}\mathrm{Y}$ using the $\mathrm{TALYS}$ code. Theoretical predictions were based on the Kopecky-Uhl generalized Lorentzian model for $E1$ transitions and the spin-flip scissors model for $M1$ transitions and optimized using a normalization factor $G_{\mathrm{norm}}=1.31$. The calculated ${}^{88}\mathrm{Y}(n,\gamma ){}^{89}\mathrm{Y}$ cross sections are in good agreement with JEFF-3.3, but show deviations from other evaluated nuclear data libraries, including JENDL-5, TENDL-2023, and ROSFOND-2010.

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• Gamma-ray strength functions
• Photonuclear reactions
• Radiative capture