The ($n,2n$) activation cross sections of ${\mathrm{F}}^{19}$, ${\mathrm{Na}}^{23}$, ${\mathrm{Mn}}^{55}$, ${\mathrm{In}}^{115}$, and ${\mathrm{Ho}}^{165}$ have been measured in the neutron energy range from 12.7 to 19.4 MeV. In addition, the activation cross sections for the ${\mathrm{In}}^{115}(n,n^{\prime }){\mathrm{In}}^{115m}$ and ${\mathrm{Al}}^{27}(n,\alpha ){\mathrm{Na}}^{24}$ reactions have been measured in the energy range from 1.0 to 19.4 MeV and from 6.1 to 19.4 MeV, respectively. Most of the measurements were made relative to the fission cross section of ${\mathrm{U}}^{235}$. The experimental ($n,2n$) cross sections have been compared with the predictions of the semiempirical cross-section theories of Pearlstein and of Gardner.

• Received 29 June 1967

DOI:https://doi.org/10.1103/PhysRev.163.1308