Precision Determination of Photoneutron Thresholds

Abstract

The photoneutron thresholds for ${\mathrm{C}}^{12}$, ${\mathrm{N}}^{14}$, ${\mathrm{O}}^{16}$, ${\mathrm{Cu}}^{63}$, and ${\mathrm{Ag}}^{109}$ were determined by measurement of the yield of activity as a function of the peak bremsstrahlung energy. Measurements of the photoneutron thresholds of ${\mathrm{C}}^{12}$, ${\mathrm{N}}^{14}$, and ${\mathrm{O}}^{16}$, which could be calculated accurately from the mass data, served to determine the energy scale. The photoneutron thresholds for ${\mathrm{Cu}}^{63}$ and ${\mathrm{Ag}}^{109}$ were found to be 10.61±0.05 Mev and 9.07±0.07 Mev, respectively.