14-Mev-Neutron Production Of Isomeric States For Several Rare-Earth Elements

Fast-neutron cross sections have been determined for the following reactions, using 14-MeV neutrons from the ${\mathrm{H}}^{3}(d,n){\mathrm{He}}^{4}$ reaction: ${\mathrm{Y}}^{89}(n,{n}^{\ensuremath{'}}\ensuremath{\gamma}){\mathrm{Y}}^{89m}$, 400 mb; ${\mathrm{Nd}}^{142}(n,2n){\mathrm{Nd}}^{141m}$, 545 mb; ${\mathrm{Sm}}^{144}(n,2n){\mathrm{Sm}}^{143m}$, 400 mb; ${\mathrm{Yb}}^{159}(n,2n){\mathrm{Tb}}^{158m}$, 160 mb; ${\mathrm{Er}}^{168}(n,2n){\mathrm{Er}}^{167m}$, 190 mb. Possible sources of error affecting the cross-section measurements have been discussed and evaluated numerically. The over-all accuracy was determined to be about \ifmmode\pm\else\textpm\fi{}12%.