Photoneutron Cross Sections for ${\mathrm{As}}^{75}$, ${\mathrm{Ag}}^{107}$, and ${\mathrm{Cs}}^{133}$

Photoneutron cross sections, including $\sigma \left[\right(\gamma ,n)+(\gamma ,pn\left)\right]$ and $\sigma (\gamma ,2n)$ for ${\mathrm{As}}^{75}$, ${\mathrm{Ag}}^{107}$, and ${\mathrm{Cs}}^{133}$, and $\sigma (\gamma ,3n)$ for ${\mathrm{Cs}}^{133}$, were measured as a function of photon energy from threshold to 30 MeV. The photon energy resolution varied from less than 300 keV at the lowest to 400 keV at the highest energies. The source of radiation was the monoenergetic photon beam obtained from the annihilation in flight of fast positrons. The data were taken at 300-keV intervals. The partial cross sections were determined by neutron-multiplicity counting, and the average neutron energies for both single- and double-photoneutron events were determined simultaneously with the cross-section data by the ring-ratio technique. Nuclear information extracted from the data includes giant-resonance parameters, integrated cross sections and their moments, symmetry energies, quadrupole moments, and level densities. The mass of ${\mathrm{Ag}}^{105}$ was determined from the ${\mathrm{Ag}}^{107}(\gamma ,2n)$ threshold energy. No marked structure was observed in the total photoneutron cross sections, although small deviations from a smooth curve are present, both in and above the giant resonance.