Photoneutron Thresholds for Iron, Germanium, Rubidium, and Hafnium

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.