Photoneutron Thresholds for Iron, Germanium, Rubidium, and Hafnium

Abstract

Photoneutron thresholds for ${\mathrm{Fe}}^{56}$, ${\mathrm{Fe}}^{57}$, ${\mathrm{Ge}}^{73}$, ${\mathrm{Rb}}^{85}$, ${\mathrm{Rb}}^{87}$, ${\mathrm{Hf}}^{177}$, and ${\mathrm{Hf}}^{179}$ have been measured by using bremsstrahlung from a 22-Mev betratron as a photon source. The photon-induced reactions were observed by neutron detection supplemented in one case by radioactivity determinations.A comparison of these thresholds with neutron binding energies revealed that, for some of the nuclei, better agreement was obtained if formation of the residual nucleus in an excited state instead of in the ground state was assumed. The neutron binding energies inferred from these measurements are: 11.34\ifmmode\pm\else\textpm\fi{}0.10 Mev for ${\mathrm{Fe}}^{56}$; 7.85\ifmmode\pm\else\textpm\fi{}0.13 Mev for ${\mathrm{Fe}}^{57}$; 6.50\ifmmode\pm\else\textpm\fi{}0.16 Mev for ${\mathrm{Ge}}^{73}$; 10.50\ifmmode\pm\else\textpm\fi{}0.08 Mev for ${\mathrm{Rb}}^{85}$; 9.89\ifmmode\pm\else\textpm\fi{}0.05 Mev for ${\mathrm{Rb}}^{87}$; 6.70\ifmmode\pm\else\textpm\fi{}0.09 Mev for ${\mathrm{Hf}}^{177}$; and 6.52\ifmmode\pm\else\textpm\fi{}0.12 for ${\mathrm{Hf}}^{179}$.