Ytterbium ( $\gamma$ γ , 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.