Ytterbium (\(\gamma\), n) average cross-sections data near to photodisintegration reaction threshold

Abstract.

The thick foils activation technique has been applied to estimate the average cross-sections of ^168,170,176Yb \((\gamma, \mathrm{n})\) reaction near to photodisintegration threshold. The \((\gamma, \mathrm{n})\) cross-sections are derived using the integrated photon flux at any energy range from the reaction threshold to the bremsstrahlung end-point energy. The photon flux is estimated using a calibration photodisintegration set of foils and taking in advance the spectrum linearity at high energies. The p-nuclei ¹⁶⁸Yb average cross-section is \( 106 \pm 21\) mb corresponding to \(E_{\mathrm{mean}} = 10\) MeV. The ¹⁷⁰Yb average cross section is \( 117 \pm 31\) mb matching \( E_{\mathrm{mean}} = 9\) MeV while the ¹⁷⁶Yb one is \( 123 \pm 36\) mb corresponding to \( E_{\mathrm{mean}} = 8\) MeV. The experimental results associate to statistical model simulations performed by the TALYS code. The simulated data of ¹⁶⁸Yb ranges 83–139 mb, while ¹⁷⁰Yb and ¹⁷⁶Yb vary between 89–152 and 84–170mb; which agree with the measurements within uncertainties. The simulated average cross-section of ^natYb \((\gamma, \mathrm{n})\) reaction is \( 127 \pm 25\) mb corresponding to energy ranges 6.6-14 MeV. The simulation results based on Lorentzian \( \gamma\)-strength considerations with the density level of Fermi gas plus the constant temperature model are closest to the average cross-sections measured.