The (n, 2n) isomeric cross section ratios and the (n, 2n) excitation function for 197Au

Abstract

The (n, 2n) isomeric state/ground state cross section ratio σ m/σ g and the (n, 2n) isomeric state cross section σ m of 197Au have been measured in the energy range 14.2–18.2 MeV by activation techniques using a Ge(Li) detector gamma-ray spectrometer. Neutrons were produced with the 3H(d, n) 4 He reaction. The cross section ratios were determined from least squares fits to the ground state gamma activity of 196Au ( E γ = 356 keV). The absolute isomeric cross sections were determined by measuring the gamma activity of the metastable state in 196Au ( E γ = 148 and 188 keV) using the mixed-powder method with 27Al(n, α) 24 Na as the monitor reaction. The measured cross section ratios and the isomeric cross sections were found respectively to be (0.075 ± 0.003) and (152± 11)mb at (14.2± 0.2)MeV, (0.078± 0.003) and (161± 11)mb at (15.2± 0.2)MeV, (0.096 ± 0.007) and (185± 13) mb at (16.2± 0.2)MeV, (0.122 ± 0.02) and (202 ± 14)mb at (17.2 ± 0.2)MeV, and (0.124 ± 0.003) and (185 ± 13) mb at (18.2 ± 0.2)MeV. The isomeric cross section at 14.2 MeV was also measured using associated particle techniques for monitoring the neutron flux. The average cross section for three associated particle activations was (155 ± 8)mb.