Abstract
Excitation functions have been measured for the (γ, n), (γ, p) and (γ, pn+γ, 2n) reactions in 58Ni and the (γ, p) reaction in 62Ni, from threshold to 32 MeV. A preponderance of protons is found from 58Ni with the ratio integral operator032 σ(γ, p)dE/integral operator032 σ(γ, n)dE=2.35 ± 0.20.
The shapes of the (γ, n) and (γ, p) cross sections are found to be very similar, peaking near 19 MeV with widths of about 4.3 MeV. The 58Ni (γ, pn+γ, 2n) cross section increases monotonically from threshold to 32 MeV, and the integrated cross section is about 12% of the total which is integral operator032 [σ(γ, n) + σ(γ, p) + σ(γ, pn + γ, 2n)] dE=(0.84 ± 0.10) MeV barns.
The 62Ni (γ, p) reaction is found to have an integrated cross section of (0.13 ± 0.02) MeV barns and to peak at 22 MeV, with a width of about 5.2 MeV.