Systematic study of the (n, 2n) reaction cross section for¹²¹Sb and¹²³Sb isotopes

Abstract：

The cross sections of the ¹²¹Sb $ (n, 2n) $ ¹²⁰Sb ^mand ¹²³Sb $ (n, 2n) $ ¹²²Sb reactions were measured at 12.50, 15.79 and 18.87 MeV neutron energies relative to the standard ²⁷Al $ (n,\alpha ) $ ²⁴Na monitor reaction using neutron activation and offline γ-ray spectrometry. Irradiation of the samples was performed at the BARC-TIFR Pelletron Linac Facility, Mumbai, India. The quasi-monoenergetic neutrons were generated via the ⁷Li $ (p,n) $ reaction. Statistical model calculations were performed by nuclear reaction codes TALYS (ver. 1.9) and EMPIRE (ver. 3.2.2) using various input parameters and nuclear level density models. The cross sections of the ground and the isomeric state as well as the isomeric cross section ratio were studied theoretically from reaction threshold to 26 MeV energies. The effect of pre-equilibrium emission is also discussed in detail using different theoretical models. The present measured cross sections were discussed and compared with the reported experimental data and evaluation data of the JEFF-3.3, ENDF/B-VIII.0, JENDL/AD-2017 and TENDL-2019 libraries. A detailed analysis of the uncertainties in the measured cross section data was performed using the covariance analysis method. Furthermore, a systematic study of the $ (n, 2n) $ reaction cross section for ¹²¹Sb and ¹²³Sb isotopes was also performed within 14–15 MeV neutron energies using various systematic formulae. This work helps to overcome discrepancies in Sb data and illustrate a better understanding of pre-equilibrium emission in the $ (n, 2n) $ reaction channel.