(n, 2n) Reaction Cross Sections from 12 to 19.6 MeV

Cross sections for the ${\mathrm{Cu}}^{63}(n, 2n){\mathrm{Cu}}^{62}$, ${\mathrm{Zn}}^{64}(n, 2n){\mathrm{Zn}}^{63}$, ${\mathrm{Ag}}^{107}(n, 2n){\mathrm{Ag}}^{106}$ ($T_{\frac{1}{2}}=24\mathrm{}$ min), and ${\mathrm{Sb}}^{121}(n, 2n){\mathrm{Sb}}^{120}$ ($T_{\frac{1}{2}}=16\mathrm{}$ min) reactions have been measured at incident-neutron energies between 12 and 19.6 MeV. These cross sections were determined relative to the cross section for the ${\mathrm{Cu}}^{63}(n, 2n){\mathrm{Cu}}^{62}$ reaction at an incident-neutron energy of 14.4 MeV. The measurements of Bame and Perry were used to determine the angular distribution of the neutrons from the ${\mathrm{H}}^3(d, n){\mathrm{He}}^4$ reaction, which was needed in order to compute values of the relative cross sections. These relative cross sections were then expressed as absolute cross sections by using a value of 503 mb ±7.3% (the weighted mean of the measurements of several other investigators) for the cross section of the ${\mathrm{Cu}}^{63}(n, 2n){\mathrm{Cu}}^{62}$ reaction at 14.4 MeV. Some of these data are compared with the predictions of the compound-nucleus model